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RADIOPHARMACY: AN UPDATE

A TECHNOLOGIST’S GUIDE

Produced with the kind support of TABLE OF CONTENTS

Foreword 4 Andrea Santos

Introduction 6 MarieClaire Attard

Chapter 1 The History of Radiopharmacy 8 Marius Mada

Chapter 2 Theoretical Basics of Radiopharmacy 18 Zéna Wimana

Chapter 3 Radiopharmacy Design and Protection 32 Lei Li Corrigan

Chapter 4 Generators used in Nuclear 42 David Gilmore and Daniel Tempesta

Chapter 5 - and -Produced Radioisotopes 52 Sergio do Carmo and Francisco Alves

Chapter 6 Conventional 72 Lurdes Gano and Antonio Paulo

Chapter 7 PET Radiopharmaceuticals 96 Lei Li Corrigan

Chapter 8 Radiopharmaceuticals used in 104 Christelle Terwinghe and Christophe M Deroose

Chapter 9 Blood Labelling for Nuclear Imaging 114 Naseer Khan and Giorgio Testanera

Chapter 10 Good Manufacturing Practice for Radiopharmaceuticals within 124 the Hospital Environment Kishor Solanki

Chapter 11 Translational Approach to Development 138 Latifa Rbah-Vidal and Pedro Fragoso Costa

EANM TECHNOLGIST’S GUIDE 3 RADIOPHARMACY: AN UPDATE FOREWORD FOREWORD

Foreword Nuclear medicine, which encompasses the medical field of molecular imaging and therapy, brings together many disciplines, and radiopharmacy requires that , physics and medicine work together within a synergetic environment. It is undeniable that within nuclear medicine the baseline of any good procedure is the design and preparation of the radioactive pharmaceutical, referred to as the radiopharmaceutical.

After the introduction of a radio­ (EANM-TC) made a joint effort to produce radiopharmacy to the current generator- to our colleagues from the Society of pharmaceutical into clinical practice, a book entitled The Radiopharmacy. and cyclotron-produced radioisotopes, Nuclear Medicine and Molecular Imaging– it is essential that the production and This publication was intended to help conventional nuclear medicine, PET Technologist Section (SNMMI-TS) for their preparation of the radiopharmaceutical professionals from different locations and and therapeutic radiopharmaceuticals. contribution to the book. are done by highly qualified professionals, professions to optimise their practice Additionally, good manufacturing practice In addition, I am very grateful for the with a good theoretical background and in radiopharmacy. Due to the rapid (GMP), the translational approach to work of the EANM-TC editorial and highly developed practical skills. Within a evolution of nuclear medicine and its radiopharmaceutical production and to Rick Mills for his editing, reviewing and multidisciplinary team, nuclear medicine associated procedures and practices in concerns in the support throughout the entire process. technologists are professionals who radiopharmacy, the EANM-TC reached the design and workflow of a radiopharmacy Lastly, the EANM Board and the Executive are recognized for their competence in decision that it is time to revisit the topic of are explored. Office deserve my words of appreciation preparing radiopharmaceuticals and are radiopharmacy and to produce an update I would like to thank each of the authors for their support in ensuring the continuity also responsible for performing the control to the previous edition of this guide. of this book for lending their time to this of this project. Radiopharmacy: an Update tests to determine the quality of the Radiopharmacy: an Update is the project and for helping us to produce would not have been possible without the preparations. outcome of the work of the EANM- a guide that reflects their expertise. contribution of all the above mentioned. The European Association of Nuclear TC in drawing together the expertise A special word of appreciation is due to Thank you very much! Medicine (EANM) is a reference scientific of many authors in order to produce the Translational Molecular Imaging and body for the global nuclear medicine a guide that addresses a variety of Therapy Committee for their contribution community. Taking this into account, in radiopharmacy-related topics, from to this publication. Andrea Santos 2008 the EANM Technologist Committee the history and basic principles of I would also like to express my gratitude Chair of the Technologist Committee

4 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 5 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE INTRODUCTION INTRODUCTION

Introduction In 2008, the EANM Technologist Committee published a Technologist’s Guide entitled The Radiopharmacy. It is available online through the EANM website and covers topics relevant to daily radiopharmacy practice, such as design, preparation, dispensing and documentation. Since then, many radiopharmaceutical practices have changed, especially with the introduction of new radiotracers.

This year’s Technologist’s Guide includes collection of information that will prove the basics, starting from history of an essential aid in the clinical setting and radiopharmaceuticals, and proceeds to will keep the technologist up to date with the high-end radiopharmaceuticals used the latest radiopharmacy principles and in translational medicine. Illustrations practices. and tables have been included to facilitate the understanding of certain MarieClaire Attard principles. The most widely used Main-Editor on behalf of the editors radiopharmaceuticals in SPECT and PET have been dealt with separately because of the breadth of development since the previous publication in 2008. This year’s Technologist’s Guide also covers radiopharmaceuticals used in therapy. Authors from different backgrounds have contributed to the Guide, ensuring that it will be an important addition to the knowledge base required to perform radiopharmacy. It is an unmissable

6 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 7 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE THE HISTORY OF RADIOPHARMACY by Marius Mada 1 CHAPTER 1 CHAPTER 1

EARLY PIONEERS THE HISTORY OF RADIOPHARMACY Two scientists paved the way for and compounds being efficient, while others saw advantages were being developed, attention was THE HISTORY OF RADIOPHARMACY and radiopharmacy at the end of the tried in almost all areas of medicine. A in using an interval therapy, i.e. multiple, being drawn to the dangerous effects nineteenth century. Wilhelm Conrad “radium frenzy” ensued, and radioactivity regular but weaker radiation doses of radioactive substances on patients. It Roentgen (1845–1923) discovered X-rays was used for the treatment of pulmonary (fractionated radiation). For more than a was observed that following prolonged in 1895, which for the first time provided , elephantiasis and epilepsy, decade, supporters in both camps tried to exposure to radium plasters, an insight into the living body. Only a year to name just a few conditions. strengthen their position with numerous or redness of the skin occurred, culminating later, Henri (1852–1908) found Furthermore, tumours were treated with publications before the scientific dispute in malignant inflammation. «[One] knows that certain naturally occurring substances radioactive substances with promising was settled in favour of fractionated today that radium rays are able to cause emit radiation that is visible over distances results. In addition to external application, radiation [1, 2]. cells to fade and thus contribute and can penetrate black paper and by 1905 internal application of radioactive to the healing of cancerous ulcers. blacken photographic plates. Marie and materials (radium or sulphate) However, it must be remembered that Pierre discovered that and was being performed using various DANGERS OF RADIOACTIVITY other tissues besides the carcinoma are have this property and named methods of placing the substance. With the increasing use of , strongly attacked by the rays.» In addition, this phenomenon radioactivity (Fig. 1). It capsules, needles, glass tubes and other the need to protect healthcare it was observed that small mammals, soon became clear that these rays should suitable containers were used so that the professionals was soon recognised. Even such as mice, died within a few hours find application in many different scientific radiation source could be removed from today, Geiger counters and film when exposed to intense radiation [3]. fields, especially in medicine. the body once the treatment had been are standard equipment in radiology and Following the initial application of completed. The radiation treatment of nuclear medicine departments and are CULTURE X-rays in the treatment of skin diseases, tumours continued following the First not dissimilar to the devices from the past In the early twentieth century, the scientific radioactive substances were also used in World War and progress was recorded (Fig. 2). world was fascinated by the therapeutic this area. Scientific journals at the time particularly in measuring more precisely At the same time as the early devices to potential of radioactive compounds but reported successes in therapeutic hair the dose applied. Already at this stage aid protection of healthcare professionals was also aware of the dangers they can removal and treatment for acne or copper there were two approaches to treatment: rash associated with syphilis. Soon, the one group of considered a use of radioactive substances developed single, but sufficiently strong dose of into a broad experimental field, with radiation (intensive radiation) to be more

Figure 2: Left: The Hanford ring badge, used to determine exposures to the hands of workers manipulating radioactive sources. Centre: Film badge from the . Right: End-window Geiger- Figure 1: Pioneers in radiology and radiopharmacy Müller tube for measurement of radioactivity

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THE HISTORY OF RADIOPHARMACY pose. In a technical article presented at to a considerable number of spas that Up until the mid-1930s, the benefits later in the casserole. Faced with the facts, THE HISTORY OF RADIOPHARMACY the British Pharmaceutical Conference promoted their use for therapeutic of radiation for therapy were exploited the landlady could only say, “This is magic!” in 1904, the pharmacist William Harrison purposes. Especially in the United States, by the salesmen trying to trade in the He might have lost his room after this, but Martindale (1874–1933) summarised the companies started commercialising so-called universal panacea. Pharmacists the principle used by George de Hevesy existing findings on radioactivity and its radioactive drinking , promising to then started to get more involved in the was later adopted in medicine and referred application in medicine, including the rejuvenate the body, kill or purify research into radioactivity and demanded to as the “tracer principle”. A radioactive possible dangers, yet at the same time the blood (Fig. 3). Radioactive water was that the preparation of these products be substance is introduced into the human radioactivity was presented as a tried-and- also used in the food industry in recipes carried out by professionals. As a result, in body in an amount sufficiently small as not tested therapeutic method against many for biscuits or chocolate. The use of 1938 the Federal Food, and Cosmetic to interfere with the molecular processes; diseases. radioactive water at home, despite the Act (FD&C) was passed in the United States, its distribution then reflects the metabolic Backed by the scientific research and absence of scientific evidence regarding giving the Food and Drug Administration functions of the body, making this a great with a twist of entrepreneurialism, around the mechanism of cure, peaked in the early authority to oversee the safety of food, application for diagnosis and therapy. the world radioactivity was praised as a 1920s. However, the practice continued and cosmetics. This act required The prerequisites for broad application miracle cure or panacea. The discovery into the 1970s, with different brands using that the safety of all new drugs must be of the tracer principle, however, were of natural radioactive gave rise different radiation doses, some of them proved to the FDA before they could be the discovery of artificial radioactivity potentially dangerous to life. marketed to the public [4]. and the large-scale production of Other radioactive preparations such as radionuclides. The first cyclotron was globules, suppositories, lozenges, tablets developed in 1930 by Ernst Lawrence at and even injections were also available. RADIATION AND DIAGNOSTICS the University of California in Berkeley. These were advertised to increase vitality, It is possible that the introduction In December 1942, Enrico Fermi and co- promote male strength or prevent aging. of radioactivity into diagnostics was workers achieved the first self-sustained In addition, radioactive toothpaste, associated with an attempt to solve a , which led to cream, cosmetics, soap, hair culinary dilemma. The Hungarian chemist tonic and gelatin were offered for sale. George de Hevesy (1885–1966) was For the treatment of rheumatic diseases working alongside Ernst Rutherford in or to strengthen the libido, radioactive Manchester, England, and was renting preparations were integrated in the fabric a full-board room. A Sunday speciality of bedding, allowing longer exposure cooked by his landlady was meat during sleep. By 1930, however, the pudding. de Hevesy suspected the lady American authorities found that 95% of was recycling the meat from the Sunday the products they tested had no traces of meal during the following week. To prove radioactivity. It is fair to say that although this, he spiked his leftovers with a small Figure 3: 4: Ernst Lawrence developed the first such products were mis-sold, consumers amount of a radioactive that he cyclotron and Enrico Fermi was the first to create Figure 3: Advertisement for VigoRadium, water were at least spared the hazards of was eventually able to trace a few days a nuclear reactor containing radium radiation.

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GAMMA CAMERA THE HISTORY OF RADIOPHARMACY the building of the nuclear reactor (Fig. At the same time, the emission the , the field of nuclear The task of radiopharmaceutical THE HISTORY OF RADIOPHARMACY 4). Compared with the cyclotron, the tomography (PET) scanner was being medicine and its radionuclides had been pharma­cists at that time consisted mainly nuclear reactor could produce quantities developed in the United States, and by transformed beyond recognition. in the production of intravenous and oral of radionuclides millions of times greater. the mid-1980s commercial had formulations of artificial radionuclides After the Second World War, Abbott become available from CTI Corporation and testing of radionuclide purity or Pharmaceuticals started selling the first specifically for PET. Hybrid diagnostic pyrogens. Hospital pharmacists played a radioisotopes [5]. By 1947, production imaging was just around the corner, key role in the production and dispensing facilities for medical and biological with the first PET/CT scanner being of such preparations, as the short-lived radionuclides had become available developed by David Townsend and Ron radionuclides required fresh preparation outside the United States, including at Nutt in early 1990s (Fig. 7) and PET/MRI and immediate administration to the Harwell in the United Kingdom. These appearing towards the end of the decade patient. facilities mainly produced -32, [6]. By the time the first commercially With the increasing use of radio­ sodium-24 and -131. Subsequently, available simultaneous PET/MRI scanner pharmaceuticals, interest in special training more exotic isotopes were added to the was installed in 2009, half a century after also grew. In-depth knowledge and list, such as -89, -90, skills were indispensable when handling Figure 7: Ron Nutt and David Townsend, who iodine-125, -153, rhenium-186 radioactive and isotopically labelled drugs. developed the first PET/CT scanner and gold-198. In 1962, -99m Thus, the first tracer methodology courses was proposed as a radionuclide agent were held at Purdue University (West for diagnostic purposes; it was to be RADIOPHARMACY Lafayette) in 1947. In the 1950s and 1960s, extracted from molybdenum-99 in a The development of the field of the range of courses in the United States generator, and this made possible the radiopharmacy or nuclear pharmacy (in grew steadily. In the mid-1970s, the Section use of the radionuclide in many hospitals. the United States) as an independent on Nuclear Pharmacy of the American In 1957 the prototype of the gamma pharmaceutical specialisation began Pharmaceutical Association (APhA) was camera was constructed by Hal Anger in after the Second World War, mainly in founded, and in 1978 the APhA published United States using photomultipliers (Fig. the United States. A reactor was built in the Nuclear Pharmacy Practice Standards. 5). Within a decade, this instrument had Figure 5: Hal Anger, with his prototype gamma 1943 in Oak Ridge (Tennessee), and the These guidelines, which covered aspects become widely used across the globe. first radionuclides for civilian use and including definition, scope, content, Following developments in computers clinical application became available professional requirements, advanced and image reconstruction, in 1976 John there after 1945. The 15th edition of U.S. knowledge and practical implementation, Keyes developed the general-purpose Pharmacopeia was published in 1955 formed an important basis for the single- emission computed tomo­ and contained for the first time several development of the area towards a graphy (SPECT) camera that we know monographs on radiopharmaceutical special discipline. In the same year, the today (Fig. 6). preparations, for example Board of Pharmaceutical Specialties (BPS) Figure 6: John Keyes and the Humongotron SPECT camera (iodine-131) solution. recognised Nuclear Pharmacy as its first

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THE HISTORY OF RADIOPHARMACY specialty. For acquisition of certification in SUMMARY REFERENCES THE HISTORY OF RADIOPHARMACY Nuclear Pharmacy, proof of subject-related Radioactive compounds were being used training or 4000 hours of professional against many diseases as long ago as 1. Staiger C. Radiologic health. The history of radiophar- experience was required [7]. the beginning of the twentieth century. macy. Pharm Unserer Zeit 2005;34:454–459. Unlike in the United States, the Radiopharmaceutical products were 2. Sten C. A glance at the history of nuclear medicine. development of radiopharmacy in tried and tested in the treatment of skin Acta Oncol 1995;34:1095–1102. Europe entailed the creation of and and were also considered 3. Martindale WH. Notes on radioactivity. Pharm J additional further education regulations to hold promise in offering a longer 1904;73:254–258. rather than new individual specialties. and healthier life. It was clear from 4. Shaw SM, Ice RD. Nuclear pharmacy. Part I: Emer- University-based advanced, additional the beginning, however, that the line gence of the specialty of nuclear pharmacy. J Nucl Med and supplementary courses were the between the benefits and the dangers Technol 2000;28:811. dominant form of specialisation. PhDs of radioactivity is very thin. Conventional 5. Staum M. Landmarks and landmines in the early with a radiopharmaceutical focus have medicine tried to solve this balance history of radiopharmaceuticals. J Nucl Med Technol been offered in countries such as Greece, using empirical methods. The pioneers of 1992;20:209–213. Spain, Hungary and the United Kingdom. radiotherapy have to be credited with the 6. McCready RA. History of nuclear medicine in the UK. At the ETH Zurich, the postgraduate fact that their work on the biological and In: McCready R, Gnanasegaran G, Bomanji JB, eds. A course Radiopharmaceutical Chemistry/ pathochemical mechanisms of diseases history of radionuclide studies in the UK: 50th anniver- Radiopharmacy was established in the and the effect of radioactivity provided, sary of the British Nuclear Medicine Society [Internet]. mid-1990s in cooperation with the at an early stage, insights into the dangers Cham (CH): Springer; 2016:Chapter 2. Universities of Frankfurt and Leipzig. of radioactivity while also creating the 7. Graham M. Evolution of nuclear medicine training: This course is probably the most basis for modern nuclear medicine. After past, present, and future. J Nucl Med 2007;48:257–268. comprehensive of its kind to date. The the Second World War, radiopharmacy 8. Clarke L. A technologist’s viewpoint. In: McCready course follows the guidelines of the established itself as an independent R, Gnanasegaran G, Bomanji JB, eds. A history of ra- European Association of Nuclear Medicine discipline of pharmacy, initially in dionuclide studies in the UK: 50th anniversary of the (EANM) and has been recognised by the the United States and subsequently British Nuclear Medicine Society [Internet]. Cham (CH): latter. across the world. Developments in Springer; 2016:Chapter 4. The role of the nuclear medicine nuclear medicine were driven in part technologist (NMT) in radiopharmacy by the success of radiopharmacy. IMAGE REFERENCES has mirrored the development of the In this context, the nuclear medicine 1. Wikimedia field. During the past two decades, it technologist has acquired a recognised 2. https://www.orau.org/PTP/museumdirectory.htm has become a priority across the globe role in the delivery of safe and efficient 3. McCoy, B.: Quack! Tales of medical fraud from the museum of questionable medical devices. to ensure that NMTs have the necessary radionuclide diagnosis and treatment. Santa Monica 2000, pp. 95-114 4. Wikimedia training and competencies, including skills 5. J. Nucl. Med. Technol. December 1, 2005 vol. 33 no. 4 250-253 that place NMTs alongside pharmacists, 6. Portrait courtesy of Dr W L Rogers. Gantry photograph taken from J. Nucl. Med. 18 381–7 physicists and physicians [8]. 7. https://www.dotmed.com/news/story/13157/

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THEORETICAL BASICS OF RADIOPHARMACY

by Zéna Wimana

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THEORETICAL BASICS OFTHEORETICAL RADIOPHARMACY INTRODUCTION their characteristics determine the particles means that they have a lower BASICS OFTHEORETICAL RADIOPHARMACY purpose (therapy or imaging) for which LET and are thus less potent in causing Radiopharmacy is the art of preparing high-quality, radioactive, medicinal particular radionuclides are best suited. damage. However, this can also be products for use in diagnosis and therapy. The production and handling of A radionuclide can need one or multiple an advantage in terms of toxicity. The radiopharmaceuticals requires specific expertise. Different aspects need steps to reach a stable atom, leading use of β- particles for therapy is now well to be taken into consideration, including correct usage, storage of rapidly to a decay scheme containing different established and still increasing. Their lower decaying diagnostic radionuclides, disposal of when emissions. LET and longer range allow the treatment using longer-lived therapeutic radionuclides and quality controls. Alpha particles are nuclei of larger tumours compared with alpha consisting of two and two particles. To stop β- particles, a denser Unlike other appropriate radionuclide. In this context . They are heavy particles and material than paper is needed, such as modalities, PET/SPECT cannot be per­ it is to be noted, however, that a specific as a consequence of their large size Plexiglas or aluminium. In contrast to formed without radiopharmaceuticals; vector molecule is not always needed to they interact very strongly with matter, their negatively charged counterpart, β+ similarly, unlike external beam radio­ allow imaging or treatment of a specific more so than other particles, and particles are used for imaging purposes. therapy, nuclear medicine therapy cannot disease (e.g. when using iodine for deposit their energy on a short path In fact, however, it is not the β+ particles be performed without them. Accordingly, ). length [ (LET)]. themselves that are imaged, but secondary radiopharmaceuticals prepared in the Accordingly, they are much more potent emitted gamma rays: when a β+ particle radiopharmacy are the cornerstone of CHOICE OF RADIONUCLIDE for therapeutic purposes than other encounters an , a phenomenon nuclear medicine. In this chapter we The choice of radionuclide is pre­ emission types. Furthermore, with regard termed annihilation takes place, whereby will focus on the theoretical basics of dominantly based on three factors: to radioprotection they are stopped the mass of both particles is converted radiopharmacy. a. The purpose for which the without difficulty (a simple piece of paper into energy and two gamma (511 The starting point in the preparation of radiopharmaceutical is to be used will suffice), making them more difficult keV) are emitted in diametrically opposed a radiopharmaceutical always depends b. The compatibility of the radionuclide to detect. Fortunately, the alpha-emitting paths. These are the gamma photons that on the goal, i.e. what we want to see with the vector molecule radionuclides used in nuclear medicine are detected by PET. or treat. This can be the function of an c. The availability and price of the also have gamma emission in their decay Gamma rays are electromagnetic /system, a characteristic radionuclide scheme, allowing detection. To date only emissions that are used for imaging. They of a disease or a hallmark of cancer. Vector one alpha radiopharmaceutical has been have the least interaction with matter and molecules have to be used against these Purpose of using the approved for clinical use (radium-223 or thus can be detected outside the body, in targets, and have to demonstrate sufficient radiopharmaceutical­ Xofigo), but several others are either in contrast to the other types of emission. To specificity to allow an appropriate contrast. Radionuclides are unstable atoms clinical trials or under development. stop gamma rays, even denser material is The vector molecule is labelled with a that attempt to attain a stable state Beta particles are smaller charged needed, such as lead. radioactive flag, i.e. a radionuclide. This through the release of ionising energy particles and are either (β-) or An interesting and useful characteristic step in radiopharmaceutical production in the form of alpha (α), beta (β–/+) (β+). The former are used for of , or radioactivity, is is commonly referred to as radiolabelling, particles or gamma (γ). The nature of therapy and the latter for imaging. The that it can be detected and quantified. and it starts with the choice of the most each of these forms of emission and smaller size of β- compared with alpha The measured radioactivity is expressed

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THEORETICAL BASICS OFTHEORETICAL RADIOPHARMACY in the SI unit becquerel (Bq), with 1 Bq case of PET, as mentioned above, Apart from the physical nature of the Direct radiolabelling of the vector BASICS OFTHEORETICAL RADIOPHARMACY being equivalent to one disintegration it is emitted indirectly following radionuclide, its chemical nature will also molecule per second (dps). However, for historical annihilation of the β+ particle with an play a role in the choice (radiometals, Direct radiolabelling can be achieved reasons (cf. Chapter 1), the unit Curie (Ci) electron. , etc.). through either substitution or chelation is still commonly used in some countries, Substitution: An atom/group on with 1 Ci being equivalent to the Compatibility of the radionuclide with Availability and price of the the molecule is substituted by the disintegration of one gram of radium. Of the vector molecule radionuclide radionuclide. This is achieved through an note, 1 Bq is equal to 2.7×10-11 Ci and 1 Ci is Besides the type of emission, a The availability and price of radionuclides exchange between radioactive and equal to 37 GBq. radionuclide is characterised by its physical depend on their mode of production. non-radioactive groups in the molecule.

The tools employed to detect and/ half-life (t1/2), i.e. the time needed for half of While there are several naturally The exchange can be with either an anion or quantify radioactivity depend on the the atoms to decay and reach the stable occurring radionuclides, in the medical or a cation. The reaction itself is then nature of the emission and the range of state. Although short-lived radionuclides field radionuclides are synthetically called a nucleophile or an electrophile radioactivity to be measured: can be considered advantageous in terms produced by nuclear reactors, accelerators substitution, respectively. A well-known

• A Geiger-Müller tube is used for the of radioprotection, the physical t1/2 often (cyclotrons) or generators (cf. Chapters 4 example of nucleophile substitution is detection of ionising radiation (alpha, turns out to be a limiting factor. and 5). Of note, the successful application the production of 18F- 18 beta and gamma). The physical t1/2 of a radionuclide has and wide availability of conventional (FDG) with -18 ( F). • A dose calibrator is used to measure to be sufficiently long to allow (1) the nuclear medicine across the world have Chelation: A molecule can have groups gamma radiation in the higher range radiolabelling process, (2) the performance largely been based on the availability of that can chelate cations. These groups of radioactivity, such as is found in of quality control testing (excluding the molydenum -99 / technetium - 99m contain electron donors that have a free radioactive sources or generator sterility), (3) administration to the patient (99Mo/99mTc) generator. electron pair that enable coordination eluate or during the dispensing of and (4) adequate distribution of the binding (O, S and N). An example is the doses to patients. radiopharmaceutical. The last-mentioned direct radiolabelling of molecules in kits 99m • A gamma-counter is used to measure will be determined by the biological t1/2 RADIOLABELLING with Tc. gamma radiation in the lower range of the vector molecule. Consequently, to METHODS TO OBTAIN It is to be noted that in order to enter of radioactivity, such as is found in obtain satisfactory contrast and thereby RADIOPHARMACEUTICALS such reactions the radioactive should biological samples (e.g. blood). allow correct diagnosis or successful The radiolabelling method used to obtain first be in the correct ,

• A beta-counter is used to measure therapy, the physical t1/2 of the radionuclide a radiopharmaceutical is mainly dictated through either reduction or oxidation.

beta particles indirectly via a and the biological t1/2 of the radiotracer by the choice of radionuclide (see above). scintillation solution. should be compatible. An example is the Some radionuclides will allow direct Indirect radiolabelling of the vector 89 • Gamma cameras, SPECT and PET use of zirconium-89 ( Zr, physical t1/2=78 radiolabelling of the vector molecule molecule detect and quantify h) rather than short-lived -68 (68Ga, whereas with others only indirect When there is no favourable way to

emissions. While with SPECT the physical t1/2=68 min) to radiolabel large radiolabelling is possible. radiolabel the vector molecule directly, detected gamma radiation is emitted proteins such as (biological the molecule first has to be modified with

by the radionuclide directly, in the t1/2=days). a bifunctional chelator (and a spacer) to

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THEORETICAL BASICS OFTHEORETICAL RADIOPHARMACY allow radiolabelling through chelation. adopted, with sterile filtration as the final documentation of the manufacturing Kit-based synthesis BASICS OFTHEORETICAL RADIOPHARMACY The common traits required for a good step in the radiosynthesis procedure if process and the use of disposable (sterile) Kit-based synthesis consists in the bifunctional chelator are: necessary. Furthermore, everything should cassettes, allowing full recording of the reconstitution of proprietary single vials • Stable and kinetically inert: be in place to protect the operator when process and reducing the risk of cross- containing sterile, lyophilised precursor, to avoid /trans-metalation/ preparing the radiopharmaceutical (cf. contamination. Furthermore, compared buffer and scavenger. This represents an all- chelation in vivo (e.g. binding of Chapter 3). with manual synthesis, automated syn­ in-one easy-to-use approach that avoids gallium-67 citrate to transferrin) thesis offers the advantages of higher the need for expensive equipment and • Fast complexation: to allow the use of Manual synthesis reproducibility and lower radiation burden lengthy procedures. Kit-based synthesis short-lived radionuclides Manual synthesis is less and less common to the operator. This approach also permits requires limited expertise, is very safe, is • Versatile conjugation chemistry these days, but manual approaches are the fractionation and pre-concentration/ reproducible and is less cumbersome • Accessibility still employed at the start of the process purification of high amounts of incoming than the other radiolabelling approaches. of developing new radiopharmaceuticals. radioactivity. In general, the procedure for It also results in important reductions in Once the precursor has been modified, Although they have limitations in respect automated synthesis comprises the investment and production costs. to facilitate this kind of reaction a trans- of radioprotection and can be quite following key steps: The availability of a wide range of chelation occurs, whereby the radionuclide cumbersome, they offer the flexibility to such kits for different indications in is first weakly chelated to a low-affinity adapt and improve the synthesis through 1. Preparation of the GMP cassettes: combination with the generator is the chelator in the reaction medium and then a trial and error approach. Nonetheless, connect vials, perform self-tests and reason for the success of 99mTc worldwide. trans-chelated to a high-affinity chelator in manual synthesis requires specific add precursor, reagents, buffer, etc. Currently, kits are also being developed for the desired molecule. expertise, dexterity and constancy, and if 2. Radionuclide transfer from cyclotron, 68Ga, which may increase the accessibility Many different chelators have been these are lacking then the reproducibility generator or vial into the cassette of PET-based molecular imaging globally. developed, including both linear (DTPA, of the synthesis outcome will be poor. 3. Radiolabelling: chemical reaction To this day, the lion’s share of radio­ HBED-CC, etc.) and macrocyclic (DOTA, between the radionuclide and the pharmaceutical preparation in conven­ NOTA, etc.). Automated synthesis vector molecule during an incubation tional nuclear medicine is by means of Automated synthesis is based on at the desired temperature for a kit-based synthesis (cf. Chapter 6). Some the use of synthesis modules to allow certain time important steps are as follows: METHODS FOR SYNTHESISING the automation of the radiolabelling, 4. Purification of the reaction mixture: RADIOPHARMACEUTICALS purification and sterile filtration of the separation of the radiopharmaceutical 1. The generator is eluted in a vial (e.g. Indirect or direct radiolabelling methods radiopharmaceutical. of interest from the rest of the 99mTc) or activity is received in a vial can be executed by means of (a) manual, (b) Although semi-automated systems components in the reaction mixture [e.g. yttrium-90 (90Y)]. automatic or (c) kit-based synthesis. It is to with stationary tubing were used initially, (free radionuclide, buffer, etc.) by 2. The cap from the pharmaceutical be noted that, independent of the method, nowadays the systems used for automated means of - extraction or vial is removed and subsequently the vast majority of radiopharmaceuticals synthesis are easily compatible with Good high-performance liquid chromato­ swabbed with . are administered intravenously and Manufacturing Practice (cf. Chapter 10). graphy 3. The appropriate activity is added. aseptic techniques should therefore be This has been achieved thanks to on-line 5. Sterile filtration (0.22-µm filter) 4. Radiolabelling: chemical reaction 6. Ready for patient injection between the radionuclide and the

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THEORETICAL BASICS OFTHEORETICAL RADIOPHARMACY vector molecule during an incubation • The working space should be clean. radiopharmaceutical are verified as well as a. Diffusion: The radiopharmaceutical BASICS OFTHEORETICAL RADIOPHARMACY at a desired temperature for a certain • Machines should be well maintained the pharmacological ones. crosses the cell membrane passively. time, with or without shaking and calibrated. Similarly to other drugs for intravenous Diffusion is driven by the concen- 5. Ready for patient injection • Precursors and other materials should injection, the appearance and the pH of the tration difference between the two be conserved appropriately. radiopharmaceutical have to be assessed. sides of the cell membrane. Example: After any type of synthesis, the radio­ • The laminar air flow should be Appearance is assessed through visual Technegas accumulation in the pharmaceutical undergoes quality maintained and tested regularly. inspection of the radiopharmaceutical, during a ventilation study. controls (QCs). These can be quite limited, with attention to various features (e.g. b. and transport: The ra- such as for kit-based synthesis when Reception clarity, presence of particles in the diopharmaceutical accumulates in a leaflet describing the required QC is All incoming goods should pass a basic solution, colour, homogeneity). The pH cells passively, via protein channels enclosed, or rather extensive, following quality check at reception: is measured with pH indicator strips or and carrier proteins present on the the European Pharmacopoeia. a pH meter to ensure that the solution cell membrane. This phenomenon • Packaging should be inspected. is within the injectable pH range. More can also be referred to as facilitat- • Conformity assessment: Accuracy of specifically, for radiopharmaceuticals, ed diffusion. Example: Technetium QUALITY OF the information on the document­ different purities are evaluated, namely pertechnetate (99mTcO4-) accumula- RADIOPHARMACEUTICALS ation of incoming goods should be the radionuclide, chemical, radiochemical tion during examination of the thy- Although the quality of the radio­ assessed (name, quantity, activity, and bacteriological; the serological purity roid gland. pharmaceutical after radiolabelling is certificate of analysis, leaflet, etc.). may also be assessed but this is seldom often the main focus of concern, other • A swab/wipe test should be done. Table 1 provides an overview of c. Active transport: In contrast to the important points have to be kept in mind performed on delivered radio­ these purities, showing their definition, passive use of protein channels and to ensure the quality of the product. A or generators to ensure their integrity. the method of assessment and the carrier proteins, active transport re- short overview of the key components is consequences of impurities. quires energy (ATP) to allow the ra- provided below (more detail is provided Radiopharmaceutical diopharmaceutical to cross the cell in Chapters 3, 5 and 6). This discussion Quality control of drugs is of extreme membrane. Example: Radioactive relates to hospital radiopharmacies; for importance and is performed thoroughly PRINCIPLES OF ACCUMULATION iodine accumulation in the thyroid descriptions of more extensive QC systems by the pharma industry. In contrast to OF RADIOPHARMACEUTICALS gland for imaging or therapy. in GMP, please refer to Chapter 10. other drugs, most radiopharmaceuticals Radiopharmaceuticals are used in nuclear are prepared in hospital settings, outside medicine to study specific targets and d. Compartmentalisation: The radio- Workplace of the pharma industry. Furthermore, biological functions. Even though the pharmaceutical is restricted to the Within the workplace, the basic radiopharmaceuticals are the foundation number of radiopharmaceuticals could vascular compartment. Example: requirement is to ensure that the radio­ of nuclear medicine. Therefore, their be limitless, the mechanisms underlying Use of radiolabelled red blood cells pharmaceuticals are prepared under the quality and thus the implemented QC their accumulation in the are (RBCs) for determination of the blood best conditions. In particular: is of the utmost importance. In the QC, based on ten fundamental principles: pool or the investigation of occult the physicochemical properties of the bleeding.

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THEORETICAL BASICS OFTHEORETICAL RADIOPHARMACY Method of assess- BASICS OFTHEORETICAL RADIOPHARMACY Definition Effects of impurities labelled colloids for imaging of the in a patient with HER2-positive breast ment marrow. cancer. with Energy spectrum Non-beneficial and unde- g. Capillary blockage: The radiopharma- 90Y- (Zevalin) Ratio of the radioactivity of Decay assessment sired increase in radiation Radionuclide the desired radionuclide ceutical is entrapped in the capillaries against CD20 lymphocytes in lym- Differential measure- dose to the patient. to the total radioactivity, purity ments of radioactivity owing to its size. Example: Macro-ag- phoma patients. expressed as a percentage. with lead shielding Poor image quality. gregated albumin radiolabelled with 99mTc (99mTc-MAA) for perfusion Ratio of the mass of the Usually no direct impact study. CONCLUSION desired stated chemical form Colorimetric Chemical purity Possible decrease in image h. Metabolic trapping: Accumulation of Although radiopharmaceuticals are to the total mass, expressed as HPLC quality a percentage. the radiopharmaceutical is based on medicinal products, the contained the enhanced of the cell. radionuclide makes them unlike

Ratio of the radioactivity of Altered biodistribution While the radiopharmaceutical mim- any other pharmaceutical product. Radiochemical the desired radiochemical TLC Altered radiation dose icking a building /energy source Radiopharmaceuticals are unique and purity form to the total radioactivity, Radio-HPLC Poor specificity of the cell enters the cell and under- are at the core of the diagnosis and the expressed as a percentage. Poor image quality goes the first step of metabolisation therapy performed in nuclear medicine. (e.g. ), it is not com- This chapter has provided an overview of Pyrogenic response Radiopharmaceutical is Non-sterile solution can pletely metabolised and accumulates the theoretical basics of radiopharmacy, Bacteriological LAL test non-pyrogenic and without result in bacterial in the cell. The cell can demonstrate or the art of preparing high-quality, purity Bacterial culture bacteria enhanced , protein or lipid radioactive, medicinal products. Several metabolism. Example: 18F-FDG PET topics have been discussed succinctly: to investigate the enhanced glucose the radionuclide, the radiolabelling and Radiopharmaceutical is metabolism of cancer cells. synthesis methods, the quality controls Serological purity RT-PCR Can result in viral infection without virus i. binding: The radiopharma- and the principles of accumulation of ceutical is a ligand that will specifical- the radiopharmaceuticals. This discussion ly bind to a determined receptor/en- serves as an introduction to the following Table 1: The different types of purity of a radiopharmaceuticalHPLC, High-pressure liquid zyme. Example: 68Ga/177Lu-DOTATATE exhaustive chapters. ; TLC, thin-layer chromatography; LAL, Limulus amebocyte lysate; RT-PCR, ( analogue) for imaging/ reverse transcription polymerase chain reaction treatment of neuroendocrine tu- e. Cell trapping: The radiopharmaceuti- are sequestered into the spleen and mours. cal is entrapped in the organ. Exam- thus can be used to image residual or j. Ab-Ag complexes: The radiopharma- ple: While passing the spleen, RBCs ectopic spleen after splenectomy. ceutical is an or antibody will endure a stress test to ensure f. Phagocytosis: The radiopharmaceu- fragment/derivative that will recog- their integrity; if they fail the test, tical is phagocytised in the reticulo- nise and bind an with high they will remain in the spleen to die. endothelial system (RES; , spleen specificity. Examples: ImmunoPET Radiolabelled RBCs damaged by heat and ). Example: Radio- with 89Zr-trastuzumab against HER2

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RADIOPHARMACY DESIGN AND RADIATION PROTECTION

by Lei Li Corrigan

30 EANM TECHNOLGIST’S GUIDE RADIOPHARMACY: AN UPDATE 3 CHAPTER 3 CHAPTER 3

INTRODUCTION RADIOPHARMACY DESIGN AND RADIATION PROTECTION In the 1950s, hospital pharmacists started to establish facilities to handle is critical to product safety and sterility RADIOPHARMACY DESIGN AND RADIATION PROTECTION Grade 0.5 µm 5 µm radioactive materials [1]. These facilities later became radiopharmacies and assurance. Products should be prepared were separated from central as special equipment was needed A 3520 20 aseptically in a grade A environment for dispensing and radiation protection purposes. B 3520 2900 with continuous particle monitoring. Typically, a radiopharmacy is responsible for the dispensing of Isolator or restricted access barrier C 352,000 2900 radiopharmaceuticals as active ingredients for targeted radiotherapy or as system technologies, and the associated imaging agents for clinical single-photon emission computed tomography D 3,520,000 29,000 processes, should be designed so as to (SPECT) scans. Recent years have also witnessed the rapid development provide maximum protection of the grade Table 1: Maximum permitted number of A environment. of fluorine-18, -11 or gallium-68 labelled radiopharmaceuticals as particles per m3 equal to or greater than the imaging agents for position emission tomography (PET) [2]. Therefore, tabulated size (at rest) A typical radiopharmacy (Fig. 1) should more and more radiopharmacies are establishing new facilities to produce include a grade D changing room, leading tracers other than technetium-99m (99mTc). However, positron-emitting Segregation of clean rooms is achieved to a grade C production area where radioisotopes have higher energy and hence require additional radiation by maintaining a pressure cascade within at least one isolator with a transport protection. This chapter focuses more on traditional radiopharmacy design the facility between adjacent areas of chamber as a grade B environment and a for the dispensing of 99mTc tracers. different classification. Clean rooms must main chamber as a grade A environment be fully sealed to maintain the pressure are installed. Room layouts should ensure regimes and reduce ingress of particles or that personnel, material, products and RADIOPHARMACY DESIGN manufacturing practice (GMP) for medical pathogens. waste flows do not compromise product Technetium-99m has a half-life of 6 h. To products for human use. More detailed Floors, walls and ceilings in the suite integrity. A radiopharmacy should also maximise the number of doses that can be guidelines compliant with that Directive should be finished in fully welded sheet include a grade D preparation or support dispensed from one batch of product, the are used in assessing applications to vinyl, i.e. standard clean room material room with a transfer hatch linked to radiopharmacy is usually built immediately manufacturing authorities and as a basis with coving at all floor-to-wall, wall-to- the clean room. This is to ensure that adjacent to the SPECT scanner, within for inspection of manufacturers of medical wall and wall-to-ceiling junctions. Walls, materials' sanitization and transfer into the Department of Nuclear Medicine. products. floors and ceilings (including the inlet the clean room occurs under a controlled 99mTc-labelled radiopharmaceuticals can The EU GMP guideline Annex 1 defines side of air diffusers) in the suite should environment and that the flow of also be shipped for use at different the requirement for the clean controlled be designed and constructed in such a personnel and materials is segregated. A locations, and a big radiopharmacy may area where the manufacture of sterile way that the surfaces are accessible for typical entrance to a radiopharmacy clean supply tracers to up to ten hospitals within products should be carried out. Clean cleaning. All finishes in the facility should room is illustrated in Figure 2. a 1- to 2-h drive radius. rooms and clean air devices should be be compatible with the mechanical and Most radiopharmaceuticals are manu­ classified from A to D (Table 1) in accor- chemical effects of the intended methods factured and dispensed into sterile vials dance with EN ISO 14644-1:2015. EN ISO of cleaning and disinfection. before being administered by intravenous 14644-2 also provides information on test- Due to the short half-life of 99mTc, injection. Directive 2003/94/EC, adopted ing to demonstrate continued compliance radiopharmaceuticals are administered by the European Commission, lays down with assigned cleanliness classifications. before completion of a sterility test. the principles of and guidelines for good Hence, effectiveness of infection control

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RADIOPHARMACY PERSONNEL RADIOPHARMACY DESIGN AND RADIATION PROTECTION – RESPONSIBILITIES AND regularly. Some training may be carried RADIOPHARMACY DESIGN AND RADIATION PROTECTION TRAINING out in the form of group lectures: general Key management personnel of a GMP training, overview of the quality radiopharmacy include the Head of management system, policy of change Production and the Head of Quality management, how to handle deviations, Control, who must be independent etc. from each other and appointed by senior management. Senior technicians and technicians will be assigned in the RADIATION PROTECTION production team or QC team for the The Euratom/European Union Basic performance of daily tasks. In a small unit, Safety Standards Directive 2013 (BSSD) Figure 1: Layout of radiopharmacy and room a technician can be trained to carry out sets out updated safety requirements (illustrative) production and QC protocols but cannot for the nuclear and radiological sector. be involved in both production and QC Radiopharmacy should be compliant with Some radiopharmacies have dedicated for the same batch. Depending on the each country’s current ionising radiation clean rooms for blood labelling size of the unit, a separate Head of Quality regulations and health and safety procedures. In the design of the facility, Assurance and Head of Quality Unit legislation to guarantee the safety of the Figure 2: Typical entrance to a radiopharmacy adequate segregation of the tracer clean room: the clean room door is without a may be appointed. The radiopharmacy public. manufacturing process and the blood handle, a sticky mat is placed on the floor to must have an organisational chart that Radiopharmacies should gain local labelling process is very important to remove dust from shoes, there is an interlock defines every position and the managerial Regulatory Body permits for radioactivity avoid cross-contamination. This entails at the door, access to the room is restricted, hierarchy. Senior management must storage and emissions that cover bringing segregation of the flow of personnel, and a sign on the door indicates that this is ensure that the duties of those in positions radioactivity into the lab, delivery of materials and waste. a radiation control area and shows contact of responsibility are clearly defined in radioactive products to clients and Ungraded rooms may also be included details for the radiation protection supervisor their job descriptions and that adequate management of radioactive waste. for storage of materials and quality control training is provided to ensure competence Radiopharmaceuticals emit penetrating (QC) of products. The storage room, (HPLC) to measure the radiochemicaland in the execution of responsibilities. gamma radiation and high-energy fridge and freezer require continuous chemical purity, pH meter or pH paper A training plan should be defined electrons. They present an external temperature and humidity monitoring to to measure the pH value and a kit for each role. Typically, the training hazard (hand and body exposure), a ensure that materials are stored properly to test for the endotoxin level. Some in a standard operating procedure contamination hazard (primarily to the and are fit for purpose. The QC room radiopharmacies are also equipped with includes observation, performance of hands) and also an internal hazard if should be segregated from the production incubators to assist in the environmental the procedure under close supervision controls are not properly implemented. area. Typically, the following equipment is monitoring of . and performance of the procedure In the United Kingdom, the role of installed in the QC room for QC testing: independently during competency the radiation protection supervisor (RPS) thin-layer chromatography (TLC) and/ assessment. The competence of each is defined in the Ionising or high-pressure liquid chromatography staff member should be reviewed Regulations 2017. The RPS is appointed

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RADIOPHARMACY DESIGN AND RADIATION PROTECTION by the radiation employer to ensure monitoring. The location of the detectors The thermoluminescent dosimeter Active personal dosimeters (APDs) RADIOPHARMACY DESIGN AND RADIATION PROTECTION compliance with the legislation in should be determined during the design (TLD) is a type of passive dosimeter which measure the dose and dose rate (Fig. 4). respect of work carried out in an area stage of the radiopharmacy. is used to measure exposure from ionising These measurements are displayed in which is subject to local rules. The legal All persons entering the radiation radiation (Fig. 4). The TLD is normally worn real time so that the user has immediate responsibility for supervision, however, control area must wear the following on the trunk of the body but can also be feedback regarding current exposure. remains with the radiation employer. personal protective equipment: lab coat, worn on the extremities (e.g. for measuring APDs are more expensive than TLDs and Radiation protection includes different hairnet, overshoes, disposable gloves and doses to the fingers). TLDs measure the are usually worn by operators who have a aspects: the clean room should provide safety eyewear. Staff are usually required to the whole body and higher chance of being exposed to large enough shielding to ensure safe handling to wear double gloves; the outer gloves fingers over a of time. The radiation amounts of radioactivity. and storage of the radioactivity; based on are sacrificial and should be changed dose received by each staff member is Quality assurance (QA) is a broad concept the work flow, there should be efficient promptly if they become contaminated. reviewed regularly by the RPS, and if the covering every aspect that collectively or radiation monitoring equipment in place At the border of the radiation dose reaches the level warranting an individually impacts the product quality. when incidents occur; all staff should be controlled area, the changing room or investigation, a formal investigation will QA within a radiopharmacy entails the trained in good practice in the handling lobby should be equipped with the be carried out. This investigational level is establishment and maintenance of a of radioactive material (local rules); and following for emergencies: a telephone determined based on the work load and quality management system to ensure radiation risk assessment should be for communication to the RPS when an the nature of each task and should be that radiopharmaceuticals are of the performed before establishing a new incident occurs, a hand and foot monitor defined in the local rules. required quality for the intended use. QA protocol. for contamination self-check (Fig. 3), a is discussed in more detail in Chapter 10. Radiation risk assessment should sink for quick decontamination and clean Quality control includes control and

also be performed during the design scrubs and shoes to change into before 1 2 testing of raw materials, process control of the radiopharmacy and a decision leaving the contaminated area. and testing of final products. The aim is made on the level of shielding needed to ensure that the product meets the for safe handling and storage of the specification before release for use. maximum amount of radioactivity Figure 3: The QC lab in a radiopharmacy is permitted. A computerised clean room- Left: mobile usually equipped with (1) a dose calibrator contamination compatible gamma radiation detector to ensure that the dose delivered is what monitoring must be installed to provide continuous is intended and (2) a radio-TLC scanner equipment; 3 4 to determine the radiochemical purity of

right: hand and the final product. Some radiopharmacies foot monitor are equipped with a pH meter for pH measurement and HPLC with a radio detector for quantitation of chemical and radiochemical impurities. Gas Figure 4: Examples of TLDs (1, 2) and APDs chromatography can be used for the (3, 4) quantitation of residual organic solvents

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RADIOPHARMACY DESIGN AND RADIATION PROTECTION when applicable. A disposable kit has RADIOPHARMACY DESIGN AND RADIATION PROTECTION been licensed and marketed for rapid determination of the product endotoxin level by means of limulus amoebocyte lysate assay. This equipment can also be a valuable asset in the QC lab of a radiopharmacy.

REFERENCES

1. Christian JE. Radioactive isotopes in hospital phar- macy. Bull Am Soc Hosp Pharm 1950;15:52–57. 2. Paans AMJ, van Waarde A, Elsinga PH, Willemsen ATM, Vaalburg W. Positron emission tomography: the conceptual idea using a multidisciplinary approach. Methods 2002;27:195–207.

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GENERATORS USED IN NUCLEAR MEDICINE

by David Gilmore, Daniel Tempesta

40 EANM TECHNOLGIST’S GUIDE RADIOPHARMACY: AN UPDATE 4 CHAPTER 4 CHAPTER 4

INTRODUCTION GENERATORS USED IN NUCLEAR MEDICINE Radionuclide generators are a convenient way to produce and isolate column using saline (0.9%), generally with in a slightly different fashion. When one is GENERATORS USED IN NUCLEAR MEDICINE medical isotopes used in nuclear medicine. All generators work on the a volume of 5–20 mL. 99mTc, when eluted, is ready to operate the generator, a saline 99m 99m - same principle: a longer-lived isotope decays into a shorter-lived isotope, in the form Tc-pertechnetate ( TcO4 ). vial of a specific volume is applied to the which can be isolated from the generator through a process called elution. Column generators are design­ in-port and an evacuated vial of at least The rate of ingrowth by the parent is approximately similar to the ed as either liquid or solid column the volume of the saline vial is applied to decay of the daughter nuclide. The eluted isotope (eluate) can be either generators, of which the solid column the out-port. As long as the evacuated vial administered directly into patients or labelled with a drug to create a generator is the design used clinically has enough vacuum, all of the saline in radiopharmaceutical, each approach giving a desired distribution in the owing to ease of operation compared the vial will be pulled through the column body. Common radionuclide generator systems used clinically are shown with the liquid column generator. Solid and collected through the out-port. In in Table 1. column generators exist in two styles: the instance of a dry column system, the wet generators and dry generators. As volume and concentration of the eluate A few key properties are required MOLYBDENUM-99/ the names suggest, either the generator are dependent on the volume of the saline of generators in order for them to be TECHNETIUM-99M GENERATOR column remains full of saline after elution charge applied to the system. successful. First, generators must use The molybdenum-99/technetium 99m (wet) or all the saline is removed from the Yield refers to the amount of isotopes that have different chemical (99Mo/99mTc) generator is the most column after elution (dry). Wet generators daughter isotope collected after elution properties so that they may be separated widely used generator in nuclear operate by leaving a large reservoir of of a generator. Using the 99Mo/99mTc, the chemically. For medical use, only the medicine and technetium-99m (99mTc) saline connected to the in-port of the theoretical yield refers to the amount of daughter isotope is desired, and eluting is used to produce many commonly used generator and applying an evacuated vial 99mTc that could potentially be collected too much of the parent isotope can radiopharmaceuticals, as shown in Table 2. on the out-port. The vacuum on the vial from the generator based on the amount cause problems such as excess radiation With a physical half-life of 66 h, the parent pulls saline from the reservoir through of 99Mo present and the efficiency of the dose to the patient or unsatisfactory isotope, molybdenum-99 (99Mo), decays the column, washing off any99m Tc, and generator. Many factors can potentially radiopharmaceutical labelling. Generators into the shorter-lived 99mTc, which has a the resulting eluate is collected in the vial affect the yield of99m Tc from a generator. As must also be shielded properly and be physical half-life of 6 h. on the out-port. The volume, and thus previously stated, a reduction of the 99mTc portable so that they may be transported Historically, three 99Mo/99mTc gen- the concentration, depends on the size can occur. The reduced 99mTc has a higher to nuclear pharmacies and medical erator systems have been developed: col- of the evacuated vial used. After elution, affinity for alumina, and thus will be more centres that do not have a reactor or umn chromatography, sublimation and saline stays on the column, creating water inclined to stick to the column. The time cyclotron nearby. Lastly, the generator solvent extraction generators. Of these products (reducing agents) that since the last elution also has an effect must be prepared under sterile conditions three, the column generator system is the cause a reduction of the 99mTc. As a result, on yields, as the generator needs time 99 99m 99m - 99m and allow for an aseptic elution process so only type of Mo/ Tc generator currently there is less TcO4 and lower yields to “recharge” and build up enough Tc. that the radionuclide is safe to administer approved for clinical use [1]. The column during elution, making wet generators a Generally speaking, 99Mo/99mTc generators to patients. The following sections is composed of aluminum (alumina) less satisfactory choice compared with dry are most efficient when they are eluted will describe the properties of specific onto which the 99Mo is absorbed. Unlike generators. every 24 h. Lastly, physical trauma or leaks generator systems, including isotopes, 99Mo, 99mTc does not have a high affinity Dry generators tend to be more in the generator system can reduce yields. structure, operation and quality control of for alumina; therefore, as the 99Mo decays popular than wet generators and operate Two important quality control the generators. into 99mTc, the 99mTc can be washed off the

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GENERATORS USED IN NUCLEAR MEDICINE tests, known as chemical purity and rays from 99mTc and allow only the higher- (PET). The parent isotope, strontium-82 quality control after every elution. Quality GENERATORS USED IN NUCLEAR MEDICINE radionuclide purity, must be performed energy 99Mo to be measured. Once both (82Sr), has long physical half-life of 25 days control must therefore be performed at on the generator eluate. Chemical measurements have been made, a ratio and decays into shorter-lived 82Rb, which the start of the day, and not during each purity involves checking the elution can be created. has a physical half-life of 75 s. The manu- elution. for alumina which may have washed The maximum allowable amount facturer-recommended dose is 1480 MBq Quality control is performed on the off the column. Alumina present in of 99Mo breakthrough is 5.6 kBq of 99Mo per injection (1111–2220 MBq range), with generator daily before the generator is the eluate may affect the labelling of per 37 MBq of 99mTc at the time of admin- the patient typically receiving an injection used for any patients. The first elution certain radiopharmaceuticals, including istration. It is important to keep in mind for both rest images and pharmacological is discarded and the second elution is 99mTc-sulphur colloid and 99Tc-labelled that because 99Mo has a longer half-life, stress images. The 82Rb is infused at a rate used to measure contamination levels. red blood cells (UltraTag). Alumina the ratio of 99Mo to 99mTc will increase over of 50 mL/minute with a maximum of 100 The second elution is placed in a dose breakthrough testing is accomplished time as the 99mTc decays. This means that mL volume administered [2]. calibrator and measured on the 82Rb using commercially available colorimetric at the time of elution the eluate may be The generator structure consists channel according to the manufacturer’s kits that have indicators to warn when usable for patients, but as the 99mTc decays, of a shielded column with an inlet and an recommendation. Following this initial the maximum levels of alumina in an the allowable 99Mo limit may be passed. outlet line. The column is an ion exchange measurement, the elution is set aside for elution have been reached. Any elution Most radiopharmacy software systems column of tin oxide, for which 82Rb, the one hour, allowing the 82Rb to completely containing 10 µg of alumina per mL of have programs that will automatically cal- parent isotope, has an affinity [3]. Due to decay. After waiting one hour the elution 99mTc, or more, should be discarded. culate the time of eluate expiration based the low binding affinity of the daughter should be measured in the dose calibrator Radionuclide purity testing of on the measured values from the dose isotope, 82Rb, as 82Sr decays into 82Rb, the again on the 82Rb and/or 82Sr channel. the elution, also called 99Mo breakthrough calibrator. 99Mo breakthrough can occur 82Rb can be washed off the column by Ratio and correction factors are applied testing, refers to checking for 99Mo that for many reasons, including eluting with passing 0.9% NaCl through the column to determine the amount of 85Sr present may have been washed off the column saline greater than a pH of 7, excessive via the inlet line and collecting the eluate based on the amount of 82Rb in the elution. and into the eluate. Injection of excess elutions and channelling in the column, through the outlet line. The 82Sr/82Rb Records of the total volume passed 99Mo into patients is undesirable for many where only certain parts of the column generator and infusion system are shown through the generator, including quality reasons, including the additional radiation are exposed to the saline. in Figure 1. control elutions and patient infusions, dose to the patient due to the higher The short physical half-life of 82Rb must also be kept [2]. energy and longer physical half-life. The presents some challenges as far as The alert and discontinuation trigger vial of eluate is placed in a dose calibrator STRONTIUM-82/RUBIDIUM-82 elution and administration are concerned. levels for 82Sr and 85Sr breakthrough testing and measured on the 99mTc channel to GENERATOR Elution is performed with the patient’s are shown in Tables 4 and 5 respective- determine how much 99mTc is present. Rubidium-82 (82Rb), produced by the intravenous line connected directly to the ly. When alert levels are reached, quality Next, the vial is placed in a lead shield and strontium-82/rubidium-82 (82Sr/82Rb) gen- generator infusion system and the patient control testing should be performed again measured again in the dose calibrator, erator under the name Cardiogen-82® by lying on the imaging table. With the 82Rb after every 750 mL that is passed through this time on the 99Mo channel. Because Bracco, is a positron-emitting radiophar- being infused directly into the patient, the generator. When discontinuation of the difference in energy (Table 3), the maceutical used for myocardial perfusion and imaging beginning immediately trigger levers are reached, the generator lead will block out the low-level gamma imaging in positron emission tomography after injection, it is impossible to perform should no longer be used for patients.

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GENERATORS USED IN NUCLEAR MEDICINE Based on half-life and physical character- The general structure of the The parent isotope, 81Rb, has a physical agent for the treatment of non-Hodgkin’s GENERATORS USED IN NUCLEAR MEDICINE istics, the 82Sr/82Rb generator usually lasts 68Ge/68Ga is similar to other generators half-life of just 4.7 h and is produced in a . At present, 90Y is more often for 4–8 weeks [3]. in that it consists of a shielded column. cyclotron. 81mKr is produced as a gas and is used with microspheres for selective Weighing about 10 kg, this generator administered to the patient using a mask internal radiation therapy (SIRT) for liver features a glass column containing a to assess ventilation to the lungs. Technical cancer. The 90Y microspheres come in GERMANIUM-68/GALLIUM-68 titanium dioxide bed on which the 68Ge challenges exist with this generator, two varieties: resin (SIR-Spheres®) and GENERATOR is absorbed. The generator is eluted with including the 20-h expiration time due glass (TheraSphereTM). The generator Gallium-68 (68Ga) is a positron-emitting 0.1 M HCl, which washes the daughter to the short half-life of the parent isotope is produced using a Dowex 50 cation radionuclide that has gained popularity isotope, 68Ga, off the column and into the and the fact that medical centres must be exchange resin column onto which of late owing to its ability to be labelled collection vial at the end of the out-line near to a cyclotron able to produce the the parent isotope, 90Sr (half-life of 28.6 to DOTATATE and -specific mem- [4]. The 68Ge has a high affinity for titanium parent isotope. years), is absorbed. The 90Y can be eluted brane antigen (PSMA) targeting com- oxide and remains absorbed onto the The column is made of a strong using 0.03 M EDTA with an efficiency of pounds. 68Ga-DOTATATE is a somatostatin column. The generator generally has an cation-exchange resin and is eluted using approximately 98% [6]. analogue indicated for localisation of so- elution efficiency of at least 75% and can either air or when performing matostatin receptor-positive neuroendo- fully recharge every 7 h [4]. lung ventilation imaging. 81mKr can also crine tumours (NETs) using PET. 68Ga-PS- 68Ge breakthrough for this gener- be used for lung, myocardial and cerebral ZINC-62/COPPER-62 MA targeting agents are also used in PET ator is measured as the activity of 68Ge in perfusion studies. In these cases, the GENERATOR and consist of 68Ga bound to human PSMA the eluate compared with the activity of generator is eluted using an isotonic 5% Copper-62 (62Cu) has a physical half-life of ligands for the assessment of PSMA-ex- 68Ge on the column. New generators gen- dextrose solution in water [5]. 9.7 min and is being used for a number pressing tumours, such as . erally have about 3×10-5 % breakthrough of investigational research studies in PET The generator from which 68Ga of 68Ge. One situation where 68Ge break- imaging for the assessment of cardiac is produced is appealing to investigators through may increase is when the genera- STRONTIUM-90/YTTRIUM-90 and blood flow. The parent isotope, and clinicians because of the half-lives of tor goes unused for several days. In such a GENERATOR zinc-62 (62Zn), has a relatively short half- both the parent and the daughter isotope. circumstance, it is recommended that the Yttrium-90 (90Y) is a pure beta-emitting life of 9.3 h compared with other parent The parent isotope, germanium-68 (68Ge), generator be eluted with 10 mL of 0.1 M isotope with a physical half-life of 64 h, isotopes and is produced in a cyclotron. has a physical half-life of 270 days, allowing HCl one day prior to resuming clinical use making it an ideal isotope for radionuclide Because of the short half-life of the parent for a long shelf-life. The daughter isotope, of the generator [4]. therapy. Yttrium-90 is commercially isotope, this generator must be replaced gallium-68 (68Ga), has a physical half-life of available in many countries as a unit every 1–2 days 68 min, allowing for patient imaging after dose, without the need of a generator delivery from a nearby nuclear pharmacy. RUBIDIUM-81/KRYPTON-81M at the hospital or facility doing the The 68-min half-life allows sufficient time GENERATOR procedure. It can be used to label an CONCLUSION for imaging after injection while decay Krypton-81m (81mKr), with a physical half- antibody or a peptide. 90Y-ibritumomab In summary, generators allow the is sufficiently rapid to keep radiation life of 13 s and an energy of 190 keV, is tiuxetan (Zevalin) entered common delivery of short-lived medical isotopes exposure to the patient at a minimal level. most commonly used for lung imaging. use in the early 2000s as a radiotherapy to radiopharmacies and medical centres

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GENERATORS USED IN NUCLEAR MEDICINE TABLES GENERATORS USED IN NUCLEAR MEDICINE that cannot afford or are too far away from cyclotrons and reactors. In order for Table 1: Common generators used in generators to effectively deliver these Parent Half-life Daughter Half-life nuclear medicine isotopes, they must be portable, efficient, 99Mo 2.75 days 99mTc 6 h cost-effective and safe. 82Sr 25 days 82Rb 1.25 min Despite the convenience of generators, 68Ge 288 days 68Ga 68 min the parent isotopes are still created from 90Sr 28.5 years 90Y 2.67 days reactors or accelerators, which can limit 227Ac 22 years 223Ra 11 days availability. For example, while 99mTc is 81Rb 4.7 h 81mKr 13 s produced from a 99Mo/99mTc generator, the 99Mo is produced in nuclear reactors Radiopharmaceutical Use Table 2: Common by fission of -235. 99mTc radiopharma- 99mTc-macro-aggregated albumin (MAA) Lung perfusion The availability of generator-produced ceuticals and uses daughter isotopes is at the mercy of Figure 1: 82Sr/82Rb generator 99mTc-mertiatide (MAG3) Functional renal studies

the production of the parent isotope. 99m Credit: PET Study Guide, 2d ed, by Paul E. Christian and Tc-medronate (MDP) Skeletal imaging In order to keep a constant availability Nancy M. Swanston. Reston, VA: SNMMI; 2015: p. 2. 99mTc-sestamibi Myocardial perfusion studies of generators, we must continue to 99mTc-sulphur colloid Gastric emptying and lymphoscintigraphy investigate methods of production of the parent isotopes and also ensure that 99mTc-mebrofenin Hepatobiliary imaging (HIDA scan) our medical reactors and cyclotrons are reliable sources of parent isotopes. Isotope Energy (keV) Physical half-life Table 3: 99Mo and 99mTc properties 99Mo 740 and 780 66 h REFERENCES 99mTc 140 6 h

1. Phillips D. Radionuclide generator systems for nu- 5. Watson IA, Waters SL. Pharmaceutical aspects of Test Limit Table 4: Quality control alert levels for clear medicine. University of New Mexico College of krypton-81m generators. In: Cox PH, Mather SJ, Samp- 82Sr/82Rb generators Cumulative eluate volume 14 L Pharmacy. Volume V, Number 1. son CB, Lazarus CR, eds. Progress in radiopharmacy. 82Sr breakthrough 0.002 uCi/mCi 82Rb 2. Cardiogen-82 package insert Developments in nuclear medicine, vol 10. Dordrecht: 85 82 3. Yoshinaga K, Klein R, Tamaki N. Generator-produced Springer, Dordrecht; 1986:32–45. Sr breakthrough 0.02 uCi/mCi Rb rubidium-82 positron emission tomography myocar- 6. Chakravarty R, Dash A, Pillai M. Availability of yttri- dial perfusion imaging – From basic aspects to clinical um-90 from strontium-90: A nuclear medicine per- Test Limit Table 5: Quality control discontinue levels for 82Sr/82Rb generators applications. J Cardiol 2010;55:163–173. spective. Cancer Biother Radiopharm 2012;27:621– Cumulative eluate volume 17 L

4. Gallium-68 generator product information. Eckert 641. 82Sr breakthrough 0.01 uCi/mCi 82Rb 7. Christian PE, Swanston NM. PET study guide. 2nd ed. and Ziegler Eurotope. 85 82 Reston, VA: SNMMI; 2015:2. Sr breakthrough 0.1 uCi/mCi Rb http://www.radmed.com.tr/usr_img/ga_68jenerato- ru/igg100ga_generator.pdf

48 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 49 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 3 RADIOPHARMACY DESIGN AND RADIATION PROTECTION

CYCLOTRON- AND NUCLEAR REACTOR-PRODUCED RADIOISOTOPES

by Sergio do Carmo, Francisco Alves

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INTRODUCTION PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- Nuclear medicine procedures, whether production since the 1950s. Discussion average excitation potential of an atom of Range PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- performed for diagnostic or for of the working principles of cyclotrons this material. The knowledge of stopping power therapeutic purposes, rely on the decay falls beyond the scope of this work but a Stopping power values are available in variation with energy enables of a radioisotope of adequate radiation detailed description can be found in [1]. the literature for most elements and beam determination of the distance travelled by characteristics. These unstable isotopes The choice and characterisation – and energy ranges, based on experimental the beam through a medium until are not available in nature and therefore therefore determination of the feasibility measurements. Although precise complete rest, as illustrated in Figures 2 have to be artificially produced, through and yield – of a to be theoretical calculations are complex, and 3. This distance, denominated as nuclear reactions. Three main direct or performed in a cyclotron require study simpler semi-empirical expressions range, R, corresponds to the integral of the indirect nuclear processes leading to the and knowledge of physical quantities such produce a good approximation. As can inverse of the stopping power for the production of the intended radioisotopes as beam range, target material stopping been seen in Figure 1, the stopping power beam in this material, where the can be identified: power, cross section and thick target yield. decreases with the projectile energy and integration limits are the initial energy • Nuclear reactions performed in par- increases for heavier projectiles and with when entering the material, Ei , and 0:

ticle accelerators, namely cyclotrons Stopping power the medium . • Nuclear reactions performed in nu- Radioisotope production in cyclotrons Equation 2 clear reactors is based on charged projectile particles • Generators impinging on a medium containing the target material. This medium, which can be a gas, a liquid or a solid, slows down the Typically, for common energy CYCLOTRON RADIOISOTOPE particles as they penetrate. The average ranges, targets for radioisotope PRODUCTION energy degradation of the beam per unit production are: Radioisotopes can be created through length of its path in the absorbing • less that 1 cm thick when nuclide transmutation by bombarding medium, dE/dx, termed as the stopping considering solid targets, stable target nuclei with charged particles power and usually expressed in keV·µm-1, • a few centimetres long when (protons, deuterons or alpha particles). is given by Bethe’s formula: impinging on boiling liquids, These charged particles need to be • 10–20 cm long for gaseous accelerated to energies of at least several targets. MeV in order to overcome the target nucleus Coulomb barrier and lead to the Equation 1 Figures 2 and 3 show that nuclear reaction. As a result, a particle the stopping power increases

accelerator is required. Because of their where me and qe are the mass and sharply within a very short practical characteristics and high current charge of the electron, z and ν the atomic distance when the beam performance for the entire energy range number and velocity of the particles of the energy slows down almost to of interest (10–100 MeV), cyclotrons have beam, Z and N are the and rest, originating a small and Figure 1: Stopping powers in liquid water for several been almost exclusively chosen as the number of atoms per volume of the target well-defined volume where a 100 MeV particles impinging in distinct absorbing media most convenient option for radioisotope material crossed by the beam and I is the

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PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- significant amount of energy is deposited. fundamental characteristic exploited Cross section 1 barn 10-28 m2 PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- Known as the , this is the in . The cross section is the metric that Equation 4 quantifies the probability that a given Cross sections are energy dependent, Figure 2: nuclear reaction will occur, per projectile meaning that nuclear reaction probability Stopping powers and per target density unit. The cross depends on the energy of the incident in liquid water section of a nuclear reaction is usually projectile. The set of cross section values at atmospheric denominated and is defined by: for a relevant particle energy range is pressure for denominated as the excitation function of distinct energies N =N N σ the given nuclear reaction. The excitation and for different NR p target function is usually depicted as shown particles of equal Equation 3 in Figure 4 for the 68Zn(p,n)68Ga nuclear energy where NNR is the number of nuclear reaction.

reactions induced when a beam of Np

particles hits a surface with Ntargetnuclei per Thick target yield unit area. Since a projectile impinging on a target Cross section is related to event slows down as it penetrates the media, the probability and has area dimensions. It is amount of radioisotope produced by a usually expressed using the unit barn, b, particular nuclear reaction in a target can defined as: be estimated by integrating its excitation

Figure 3: Figure 4: Stopping powers Excitation function for 20 MeV pro- of the 68Zn(p,n)68Ga tons in different reaction, obtained absorbing media from experimental measurements [2–7]. The line shown is a guide for the eye

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PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- function over the range of beam energies considering the production yield without For that reason, the thick target yield is all the production possibilities and their PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- over the target material. The production taking into account its decay during the also referred to as the expected activity, optimisation, in terms of not only yield but route efficiency, termed as thick target duration, it is necessary to per unit of beam current, in saturation also radionuclidic purity of the product, it q yield Y, thus correlated to the beam consider simultaneously the production and is thus also expressed as MB /μAsat . It is mandatory to evaluate fundamental stopping power and the reaction cross rate and the decay during the irradiation has to be pointed out that a thick target parameters: sections, is defined as: to evaluate the activity produced. The yield must refer to a range of energies or • The thick target yield at saturation temporal evolution of the number N of only to an incident energy if the beam is for the intended production channel, radioisotopes in the target during completely stopped within the target. as this represents the maximum bombardment is given by: yield that can be obtained for a Equation 5 target. • Thick target yields for nuclear where N is the Avogadro number, reactions leading to radionuclidic A Equation 6

ρ is the medium density M and H are impurities: while radioisotopes respectively the atomic mass and the where I is the beam current and λ the from other elements can be target material isotopic enrichment, produced radioisotope decay constant. removed chemically, radionuclidic and C is the concentration of the target The product YI corresponds to the impurities will remain in the final nuclei in the target medium. The inverse production rate. product and therefore have to be of the stopping power multiplied by the As a result, the activity A(t) of the Figure 5: Ratio between the activity A and kept below acceptable levels. excitation function σ(E) is integrated along radioisotope produced (null at the • The evaluations provided from the rate of production YsatI, as a function of the beam energy values, from entering (Ei ) beginning of the irradiation) after an time in units of half-life the thick target yields are used

to emerging from the target (Ef ). irradiation duration t is: to determine carefully the most Although Y evaluates the absolute Equation 7 shows that a saturation Cyclotron radioisotope production: re- suitable energy range in order to number of radioisotope nuclei produced condition is reached for long irradiation search and quality control minimise radioisotope impurities, When studying distinct possible routes especially if these have longer for the production of a given radioisotope, half-lives than the intended there are several parameters that need radioisotope as they will worsen Equation 7 to be taken into account simultaneously. the radionuclidic purity with time. per incident projectile, it is more times and that the activity then tends As several different nuclear reactions • Depending on the former results, conveniently (and therefore more to equalise, asymptotically, the rate of can lead to production of the same it is also possible to establish commonly) defined as the activity production (Figure 5), since a balance is nuclide, knowledge of their excitation the target material purity to be production yield per unit of beam current reached between the number of nuclides functions is fundamental, keeping in required, concerning both the and is thus expressed in terms of MBq/µA. being produced and the decay. In such mind the practical possibilities in terms enrichment in the target nuclide conditions, a maximum producible activity of projectiles available and respective and also minimisation of specific Since there is limited interest in is obtained, which equals the product YI. energy ranges. Then, in order to compare unwanted stable isotopes.

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PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- • Such calculations must take into large quantities of 68Ge are produced Fission capture PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- account the length of typical/ by spallation reactions on RbBr targets, A nuclear chain reaction is initiated The neutrons produced in the nuclear practical according simultaneously producing high specific by the fission of a large and unstable reaction chain can alternatively originate to the half-life of the intended activity 73As as a by-product. However, target nucleus created by collision of a nuclear process denominated as radioisotope. although it is the preferred production a neutron with a heavy stable isotope. activation. In that case, • It is also fundamental to consider route for some radioisotopes and for high Fission is a nuclear mechanism that the high neutron flux is used to bombard the radionuclidic purity of the radioisotope production efficiencies, this consists in splitting an unstable a specific target nucleus. The nuclear product after the irradiation, so that is not a widely used technique because nucleus into two fragments, usually of reaction involved is usually a (n,γ) reaction, it remains in agreement with the facilities able to accelerate charged different , denominated thus resulting in a different isotope of quality control (QC) requirements particles with such a high energy are as fission pairs. Consecutive fission the target, but other elements can also sufficiently long to enable its scarce [8]. reactions are commonly observed, be produced via (n,p) or (n,α) reactions. clinical use. as the energetic fission products can A relevant illustrative example refers to 99 99 99m subsequently originate new reactions, Mo used in Mo/ Tc generators since Knowledge and simultaneous NUCLEAR REACTOR releasing more energy, gamma it can be obtained in nuclear reactors also optimisation of all these parameters are RADIOISOTOPE PRODUCTION radiation and free neutrons. A portion of through a neutron capture reaction: fundamental and equally important. It is also possible to produce radioisotopes the neutrons produced may be absorbed Failure to maintain the quality levels by bombarding target nuclei with by another starting stable nucleus and n + 98Mo 99Mo + definitively discards a production route neutrons from a nuclear reactor. Common trigger further fission events, with the Equation 9 regardless of its production yield. nuclear reactors are known for their use release of more and more neutrons. An for energy purposes – neutrons are used adequate choice of the starting stable Analogously to what happens in to generate heat that is further passed to material guarantees a self-sustained reactions, the production Spallation a fluid – but some are alternatively used nuclear chain reaction. Such a starting of radioisotopes through neutron While nuclide transmutation through to produce radioisotopes for medical use. material is denominated as fissile nucleus irradiation is influenced by the irradiation charged particle bombardment occurs In either case, and despite such distinct (e.g. 235U or 239Pu). parameters, namely: with energies up to 100 MeV, a distinct purposes, nuclear reactors invariably As the resulting smaller nuclei can be nuclear process can become relevant consist of devices able to initiate and chemically separated, this mechanism • Energy of the neutrons for higher particle energies. Typically control the creation of neutrons through can be used to produce radioisotopes. For • Neutron flux at energies higher than 100 MeV, the a self-sustained nuclear chain reaction. instance, the fission process generated • Target material emission of nuclei from a heavy target Although a detailed description of the from unstable 236U, where 235U is the • Activation cross sections nucleus in a process named spallation working principle of a nuclear reactor fissile nucleus, enables the production is likely to occur. The yield of the is beyond the scope of this work, it is of the medically relevant 99Mo, used in As illustrated in Figure 6, activation intended radioisotope and its purity are relevant to describe the fundamental the production of 99Mo/99mTc generators, cross sections vary significantly with the significantly influenced by the choice of nuclear reactions beyond radioisotope through the nuclear reaction: neutron energy, usually being much the heavy target nucleus. For instance, production. larger for low energies. As a result, neutron moderators such as water are used to Equation 8

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PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- change the energy spectrum of the atoms, Φ the neutron flux in neutrons/ obtained from decay of the latter, through 68Ge/68Ga generator system (270.8 PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- fast neutrons produced from the fission cm2/s, σ act the cross a process of elution. The radioactive day half-life compared with 67.8 process, slowing them down into lower section (for the average neutron energy) parent nuclide is previously produced min). This sort of generator generally 2 (usually named thermal) energies at which in cm , NT the number of target nuclei and though either reactors or charged particle offers limited activity but is also nuclear reaction probability is higher. λ the decay constant of the radioisotope nuclear processes (e.g. 99Mo and 68Ge characterised by a longer useful half- produced. respectively). Generators are widely used life of the device (due to the long The activity S, expressed in for several purposes, ranging from single- half-life of the parent nuclide). Bq/g, produced after an photon emission tomography (SPECT) irradiation of length t is given and positron emission tomography (PET) 2. In contrast, if the parent half-life is by: diagnostic techniques (e.g. the 99Mo/99mTc not substantially longer than that of and 68Ge/68Ga systems respectively) to the daughter, transient equilibrium (11) therapy (e.g. the 188W/188Re generator). occurs. As the activity of the daughter

Elution can be performed repeatedly increases due to the decay of the Equation 11 as the decay of the parent radioisotope parent nuclide, the attenuation of Equation 11, where A is the replenishes the amount of daughter the activity of the parent nuclide target atomic weight, shows nuclei, although the maximum activity begins to be non-negligible (Figure that, for long irradiations, the of daughter radioisotope is determined 7). A maximum activity of the activity is only limited by the and limited by the activity of the parent daughter radioisotope is reached neutron flux of the reactor. radioisotope. after about 4 of its half-lives since It is possible to classify generators the last elution [12]. The 99Mo/99mTc Figure 6: Excitation function of the according to the difference between the is the most widespread example 89Y(n,γ)90Y reaction [9–11] half-lives of the parent and the daughter of such transient equilibrium: the radioisotopes: 6-h half-life of 99mTc means that maximum activity is reached after The analogy with charged particle Generators 1. If the half-life of the parent approximately 24 h, making such reactions remains when evaluating the A generator consists of a radioactive radioisotope is much longer than a system very convenient in that it production yields in activation reactions. source providing a shorter half-life that of the daughter radioisotope, so- allows a single daily elution at a fixed In this latter case, the activation evolution radioisotope in a chemical form suitable called secular equilibrium is reached: time (Figure 8). with time is defined by: for consideration as a starting material for the activity of the daughter reaches radiolabelling. Such systems enable the the activity of the parent as long as Gamma ray spectrometry (10) separation and extraction of the intended sufficient time is allowed between Regardless of the nuclear production shortlived radioisotope (called the elutions (typically a few half-lives of process involved, it is fundamental to Equation 10 daughter) from a long-lived radioisotope the daughter), as depicted in Figure assess the quality of the radioactive where N(t) is the number of active (called the parent), the former being 7. This is, for instance, the case for the product manufactured by identifying and

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PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- The gamma ray emissions are PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- detected, analysed and recorded with an analytical spectroscopy system based on a gamma radiation detector, usually a high-purity germanium detector (HPGe), that elaborates a gamma- ray energy spectrum (Figure 9). As several radioisotopes contribute to the spectra, with a wide range of activities and characteristic gamma Figure 7: Evolution of the activities of the parent and daughter

ray intensities, it is necessary radioisotopes for the 99mTc/99Mo (red curves) and 68Ga/68Ge (blue curves) generators to acquire several spectra at distinct hours and/or days after EOB depending on the half-lives of the radioisotopes involved. Some short half-life and/or high-activity radioisotopes can initially completely mask other characteristic gamma rays, which in turn may be detectable or even predominant after an appropriate cooling time. Figure 9 illustrates such a phenomenon by presenting HPGe spectra of cyclotron-produced 68Ga Figure 8: 99mTc activity profile with consecutive elutions every 24 h, at distinct cooling times and i.e. once a day at a fixed time. Note that the maximum 99mTc activi- showing that the radionuclidic ties are obtained 23 h after each elution impurities 66Ga and 67Ga are quantifying all the radioisotope present branching ratio, emitted as they decay. detectable only several hours in the final product. For this purpose, Table 1 illustrates this intrinsic feature by after EOB, after almost total decay the radioisotopes produced are presenting the characteristic gamma rays Figure 9: Gamma ray spectra from cyclotron-pro- of 68Ga. 68 identified by their characteristic gamma from the 66Ga, 67Ga and 68Ga radioisotopes duced Ga at distinct cooling times rays, of specific energies and intensity of gallium.

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THE ILLUSTRATIVE CASE OF PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- 68GA • The relatively short half-life of the available but it has not been a preferred radioisotopic impurities 66Ga and 67Ga. PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- For most radioisotopes, more than one parent nuclide, 68Ge, significantly production route owing to technical and These are due to: production technique can be used. Each limits the useful half-life of the radioprotection issues concerning solid • residual contamination of the target production route presents advantages device to about one year. target-based production techniques and material enriched 68Zn with residual and there is generally at least one suitable • There is limited activity per elution the related low availability of facilities percentages of other radioisotopes option for each particular radioisotope. and decreasing eluted activity with such capability. of zinc, namely 67Zn and 66Zn, For instance, 90Y is almost exclusively throughout the generator lifetime. As a result of recent developments • undesired nuclear reactions that produced via nuclear reactors while 18F • The down-time between elutions involving production through liquid take place simultaneously with the is commonly obtained worldwide using (about 3–4 h) is non-negligible and targets, cyclotron-produced 68Ga has 68Zn(p,n)68Ga reactions. medical cyclotrons. The case of 68Ga is limits use on a daily basis. become a viable alternative [13, 14] to particularly illustrative of such diversity • There is a continuous possibility of generators and has been increasingly Gallium-66 is produced through as it is available through a 68Ge/68Ga breakthrough of the parent nuclide, implemented in the worldwide installed 66Zn(p,n)66Ga and 67Zn(p,2n)66Ga nuclear 68 18 67 generator (in this case the parent nuclide, Ge. “medical cyclotrons” dedicated to F reactions, whereas Ga is obtained from 68Ge, is usually obtained through a • Metallic contaminants may be production. 67Zn(p,n)67Ga and 68Zn(p,2n)67Ga nuclear charged particle nuclear reaction) and present. Direct cyclotron production of 68Ga reactions. Since both 66Ga and 67Ga have is also produced directly with charged • As the demand for 68Ga is increasing presents several advantages over the a longer halflife than the desired68 Ga, particle nuclear reactions (using either vastly, the availability of such 68Ge/68Ga generator system: their presence will affect the radionuclidic solid or liquid targets). generator systems is becoming • Larger activities of 68Ga are obtained. purity of the accelerator-produced Concerning the 68Ge/68Ga generator, an issue and advance planning of • Consecutive productions are 68Ga, which will also deteriorate with 68Ga is conveniently obtained in 0.1 M HCl purchase is mandatory to prevent possible without downtime. time since 68Ga decays faster. However, 68 as Ga(Cl3) by elution of the generator a shortage. • Running costs are affordable. although inevitable, the presence of matrix containing the 68Ge. This technique • The price is high. • Production is decentralised, and the radioimpurities 66Ga and 67Ga can presents undeniable advantages with potentially boosted by already be minimised by carefully selecting 68 68 respect to other Ga production routes: On the other hand, Ga(Cl3) is also existing biomedical cyclotron fundamental production parameters: • It is a convenient source of 68Ga for available using accelerator-produced infrastructure. • The production of 66Ga via the daily use, lasting for months. 68Ga. While the production of the parent • Independence from 68Ge production 67Zn(p,2n)66Ga reaction can be • It enables independence from 68Ga nuclide, 68Ge, for 68Ge/68Ga generators centres avoids possible shortages. minimised if the incident production centres. requires mid-energy cyclotrons, 68Ga can • No long half-life contaminants are beam energy is kept below the 13.0 • It can be used several (although be directly obtained from low-energy present in the eluate. MeV threshold of this particular limited) times per day. biomedical cyclotrons, namely via the As the manufacturing technique for nuclear reaction (Figs. 10–12). proton-induced 68Zn(p,n)68Ga nuclear direct production of 68Ga differs from • The production of 67Ga via the However, the generator system reaction on 68Zn. This process, involving the generator system, the production 68Zn(p,2n)67Ga reaction can be also presents some non-negligible the irradiation of a solid target containing considerations and concerns are distinct. minimised if the incident proton inconveniences: 68Zn, has long been established and For instance, the radioimpurities present beam energy is kept below the 12.0 in the latter case correspond only to the MeV threshold of this particular

64 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 65 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 5 CHAPTER 5

PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- nuclear reaction (Figs. 10–12). PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- • The production of 66Ga via the 66Zn(p,n)66Ga reaction can be minimised by minimising the amount of 66Zn present in the enriched 68Zn used (Figs. 11, 12). • The production of 67Ga via the 67Zn(p,n)67Ga reaction can be minimised by minimising the amount of 67Zn present in the enriched 68Zn used (Figs. 11, 12). • Since 66Ga and 67Ga have longer 68 half-lives than Ga and the Figure 10: Thick targets yields at saturation 68 production yield of Ga reaches (solid curves) for the production of 66Ga, 67Ga saturation long before the yields of and 68Ga from a typical proton irradiation of 66 67 Ga and Ga, shorter irradiations are a liquid target with 68Zn and excitation func- Figure 11: Activity ratio of the radioisotopes Figure 12: Activity ratio of the radioisotopes of preferred. tions (open symbols) of the different nuclear of Ga produced during and after a typical Ga produced during and after a typical irradia- nat reactions involved (data from [14]). irradiation of a liquid target containing Zn, tion of a liquid target containing enriched 68Zn for distinct impinging energies Although some quality control (QC) (made of 95% 68Zn, 0.5% 67Zn and 2% 66Zn), for parameters are naturally common to all in liquid targets. Table 2 illustrates distinct impinging energies manufacturing processes, such as half-life the differences by presenting the determination and pH, it is mandatory to specifications relating to radionuclidic establish some other tests to reflect the purity for both cases. specificity of each production technique. Consequently, the monograph from the European Pharmacopoeia entitled Gallium (68Ga) chloride solution for radiolabelling [15], designed to cover the 68Ga obtained from 68Ge/68Ga generators, is inadequate for accelerator-produced 68Ga. Another document, Gallium (68Ga) chloride (accelerator-produced) solution for radiolabelling [16], was specifically published to address 68Ga produced

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Main characteristic gamma rays REFERENCES PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- Half-life PRODUCED RADIOISOTOPES CYCLOTRON- AND NUCLEAR REACTOR- Energy (keV) Branching ratio 10. Tolstikov VA, Koroleva VP, Kolesov VE, Dovbenko 1. Alves F. Cyclotron and radionuclide production AG. Radioactive capture cross section for fast 511 114 % In: Pedroso de Lima JJ, ed. Nuclear Medicine neutrons by isotope Y-89. Soviet Atomic Energy Physics. CRC Press, 2011; 968. 833 5.9% 1969;26:82. 2. Hermanne A. Private communication EXFOR 66 11. Bergman AA, Kapchigashev SP, Shapar AV. Neu- Ga 9.49 h 1039 37% database 1997;entry D40930092. tron capture cross-sections for yttrium in the 2190 5.3% 3. Zhuravlev YY, Zarubin PP, Zeic YV, Kolozhvari energy region up to 50 keV. Yaderno-Fizicheskie AA, Chelgunov IV. Excitation functions of (p,n) 2751 22.7% Issledovaniya Reports, No.3; 1966:9. reactions on nuclei of isotopes Zn from E(p)=5.6 12. Abrunhosa A, Prata MI. Radiopharmaceuticals: 93.3 70.6% To 6.8 MeV. Izv Rossiiskoi Akademii Nauk Ser Fiz development and main applications In: Pedroso 1995;59:118. 184.8 21.3% de Lima JJ, ed. Nuclear Medicine Physics. CRC 67Ga 3.26 days 4. Vinogradov VM, Zhuravlev YY, Zarubin PP, Press, 2011; 95132. 300.2 16.6% Kolozhvari AA, Sergeev VO, Sitnikova IV. Exci- 13. Alves F, Alves VHP, Neves A, do Carmo SJC, Na- 393.5 4.59% tation functions of (p,n) reactions on zinc iso- tergal B, Hellas V, et al. Cyclotron production of topes in the range of E(p) from 4.9 to 5.9 MeV. 511 178% Ga-68 for human use from liquid targets: from Izv Rossiiskoi Akademii Nauk Ser Fiz 1993;57:154. theory to practice. AIP Conference Proceedings. 68Ga 67.8 min 1077 3.24% 5. Hermanne A, Walravens N, Cicchelli O. Optimi- 2017;1845:20001–20005. zation of isotope production by cross section 1883 0.142% 14. Alves F, Alves VHP, do Carmo SJC, Neves ACB, determination. In: Quaim SD, ed. Silva M, Abrunhosa AJ. Production of copper-64 for and technology. Proceedings of an and gallium-68 with a medical cylotron using 66 67 68 international conference, held at Jülich, Federal Table 1: Characteristic gamma ray lines emitted by the Ga, Ga and Ga radioisotopes liquid targets. Mod Phys Lett 2017;32:1740013. Republic of Germany, 13–17 May 1991. Berlin of gallium 15. European Pharmacopeia. Gallium (68Ga) chlo- Heidelberg New York: Springer; 1991:616–618. ride solution for radiolabelling. Available online: 6. Levkovskij VN. Activation cross section nuclides http://online.edqm.eu/EN/entry.htm of average masses (A=40-100) by protons and 16. European Pharmacopeia. Gallium (68Ga) Chlo- alpha-particles with average energies (E=10-50 ride (accelerador-produced) solution for radio- MeV). In: Activation cross section by protons labelling. Available online: http://radiofarmacia. and alphas. Moscow, 1991. org/wp-content/uploads/2018/10/MONO- Radionuclidic testing specifications 7. Tarkanyi F, Szelecsenyi F, Kovacs Z, Sudar S. Ex- GRAF%C3%8DA-GA68Cl.pdf (accessed on 2 citation functions of proton induced nuclear May 2019). reactions on enriched 66Zn,67Zn and 68Zn 68 68 68 From Ge/ Ga generators Accelerator-produced Ga production of 67Ga and 66Ga. Radiochim Acta 1990;50:19–26. 68Ga activity Minimum 99.9% Minimum 98.0% 8. Jamriska DJ, Peterson EJ, Carty J. Spallation pro- duction of neutron deficient radioisotopes in North America. In: Hardy CJ, ed. Second inter- 68 Ge activity Maximum 0.001% n.a. national conference on isotopes; Sydney, NSW (Australia); 12-16 Oct 1997. Sutherland, NSW, 66Ga and 67 Ga n.a. Maximum 2.0% Australia: Australian Nuclear Association Inc.; 1997:220–224. Other radioimpurities n.a. Maximum 0.1% 9. Stupegia DC, Schidt M, Keedy R, Madson AA. Neutron capture between 5 keV and 3 MeV. J Table 2: European Pharmacopoeia’s radionuclidic specifications for accelerator produced68 Ga and Nucl Energy 1968;22:267–281. for 68Ga from 68Ge/68Ga generators [15, 16]

68 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 69 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 3 RADIOPHARMACY DESIGN AND RADIATION PROTECTION

CONVENTIONAL NUCLEAR MEDICINE RADIOPHARMACEUTICALS

by Lurdes Gano, Antonio Paulo

70 EANM TECHNOLGIST’S GUIDE RADIOPHARMACY: AN UPDATE 6 CHAPTER 6 CHAPTER 6

RADIOPHARMACEUTICALS PREPARATION OF RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE A radiopharmaceutical is a pharmaceutical preparation that has a gressed with the design of new ligands RADIOPHARMACEUTICALS RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE radionuclide in its composition. Radiopharmaceuticals are used in that afforded 99mTc complexes with Radiopharmaceutical preparation should nuclear medicine mainly for diagnosis but also for therapeutic purposes. well-characterised molecular structures. be performed in high labelling yield They are almost invariably administered intravenously, although there are Those studies led to the development of and should provide a final product with a few oral radiopharmaceuticals and even fewer gaseous preparations. the so-called second generation of 99mTc high radiochemical, chemical, physical Also, intradermal/subcutaneous injections are used when administering radiopharmaceuticals, which includes and microbiological stability, taking into radiopharmaceuticals for sentinel node detection. brain and cardiac imaging agents such as consideration the following objectives: 99mTc-hexamethylpropylene amine oxime (1) safety for both the patient and the A radiopharmaceutical can be a early 1970s, the introduction of the (HMPAO) and 99mTc-methoxyisobutyliso- operator personnel; (2) efficacy to ensure simple chemical species such as the lyophilised diethylenediamine penta- nitrile (MIBI). The more recent 99mTc radio- relevant diagnostic information or ions 131I-, 201Tl+ and 223Ra2+, which are acetic acid (DTPA), pre-mixed with pharmaceuticals correspond to the gen- optimal therapeutic effect; (3) uptake at supplied as the salt forms Na131I, 201TlCl stannous tin to reduce pertechnetate, was eration of target-specific radiopharma- the site of action to effectively target the 223 and RaCl2, respectively. However, most a remarkable event that implemented the ceuticals based on selected biomolecules required organ or system and remain radiopharmaceuticals have two basic use of 99mTc compounds based on kits. for specific delivery of the radionuclides there for sufficient time [2, 3]. components: a chemical moiety, carrying Since then, due to the highly versatile to biological targets such as or The special characteristics of radiophar- or not an active biomolecule, and a chemistry of 99mTc, it has been possible receptors associated with disease. The maceuticals introduce some problems suitable radionuclide. The radionuclide to develop a variety of 99mTc compounds design of these radiopharmaceuticals re- that are quite unusual when compared provides the signal for detection outside useful for many diagnostic procedures. quires that the labelling procedure does with non-radioactive pharmaceuticals. the body, after administration, permitting The first generation of 99mTc radiophar- not affect the biological activity of the Most of these problems relate to the assessment of the morphological maceuticals was developed by taking biomolecule. The most common strategy stability of the preparation and are due structure or the physiological function of advantage of intrinsic properties (e.g. comprises four components: a target-spe- to the low concentration of the active the target organ or system. When used for size, form, polarity) of the 99mTc com- cific vector (e.g. monoclonal antibodies compound. Furthermore, the expected therapy, radiopharmaceuticals can deliver pounds that determine their absorption, or their fragments, bioactive peptides), a radioactivity at the dispensing time may a radiation dose to target tissues [1–3]. distribution, metabolism and bifunctional chelator, a linker and the ra- not be available owing to not only the In spite of the increased use of after administration. Most of these radio- dionuclide. The bifunctional chelator has radioactive decay but also adsorption radiopharmaceuticals based on positron- pharmaceuticals are still in use in nuclear the dual function of binding the 99mTc (or or volatilisation of the radionuclide. The emitting radionuclides for PET imaging, medicine departments. They include the any other radiometal) and incorporating masses of radionuclides in a typical radio- technetium-99m radiopharmaceuticals 99mTc-phosphonates, 99mTc-DTPA, 99mTc-col- a chemically reactive functional group to pharmaceutical are very small, so they are still have an important role in conventional loids and 99mTc-macroaggregates of albu- attach the biomolecule responsible for likely to adhere to vial surfaces. Moreover, nuclear medicine owing to the availability min (MAA) for imaging of bone, , the biological specificity of the final99m Tc high specific activities and high radioac- and affordability of the molydenum-99/ and lung perfusion, re- compound. tive concentrations may be responsible technetium-99m (99Mo/99mTc) generator spectively. for degradation by radiolysis. High dilu- and the wide variety of kits for preparation The search for new and more effica- tion can also induce stability problems. of the final radiopharmaceutical. In the cious 99mTc radiopharmaceuticals pro- Therefore, the concentration of the final

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RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE solution has to be optimised. Certain ceutical. The most common are those for each one. The amounts of Sn2+ and li- act as stabilisers, forming a protec- RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE compounds protect against radiolysis as labelling with 99mTc. gand in the kit are very important since tive colloid on the primary particles. they act as scavengers for the free radicals The widespread use of kits is related too much tin induces hydrolysis of tin Fillers are used to improve the aspect produced by the internal radiation. Ben- to their availability; their rapid and easy and consequently the production of of the lyophilised kit; zyl alcohol, a common preservative used preparation; the closed procedure for kit hydrolysed-reduced 99mTc, which may and mannitol are the most common. to prevent microbial contamination, also radiolabelling; the stability, sterility and compete with the formation of 99mTc Transfer chelators are additional li- acts as a scavenger. pyrogen-free quality of the main starting complex. Too little tin, on the other gands added to the kit formulation to Radiopharmaceutical preparations also reagents; and the reproducibility, reliabil- hand, may lead to incomplete reduc- maximise the yield of the desired com- include suspensions of aggregated par- ity and long shelf-life of the reagent mix- tion of pertechnetate to the required plex formation through the process of ticles. Particles should be prepared with ture. Generally, the kit vials contain all the oxidation state and consequently an ligand exchange. Ligands which form non-toxic, non-antigenic and biodegrad- components for the formulation, either unreliable yield of 99mTc complex. weak 99mTc complexes like gluconate, able materials, most frequently human se- solutions or suspensions, with the excep- • Additives: Additives or preservatives tartrate and citrate have been used. rum albumin (HSA). The methodology for tion of the radionuclide. Lyophilisation is are added to kits to ensure their sta- These ligands are used in cases of slow production of aggregates involves the de- performed to render the freeze-dried mix- bility and efficacy. They must not re- complex formation relative to the for- naturation of HSA solution chemically or ture ready for solubilisation in aqueous act with any other ingredient of the mation of hydrolysed-reduced 99mTc, as by heating. The main disadvantage of the solution. Typically, radiolabelling is accom- radiopharmaceutical and should pre- exemplified below for radiolabelling of preparation is that particle size and shape plished simply by addition of the radionu- vent its degradation. They include an- 99mTc-mercaptoacetyltriglycine (MAG3) 99m - 99m are not well defined. The principal consid- clide, e.g. TcO4 . Boiling may be required tioxidants, buffers, solubilising agents, and Tc-tetrofosmin. erations to take into account with these for some preparations. fillers and transfer chelators. Antioxi- preparations are the number of particles dants avoid degradation by oxidation and the size of particles. Too few particles The purpose and nature of the 99mTc kit since they compete with reductant to MOST COMMON DIAGNOSTIC lead to unsatisfactory results, whereas too components are as follows: react with oxygen accidentally intro- RADIOPHARMACEUTICALS many may be hazardous to the patient. • Ligand: This is the most important duced into the preparation. They may Currently, most 99mTc radiopharmaceuticals Larger particles may block some of the constituent of a technetium cold kit also help in reductant conservation are still of the first- and second-generation greater blood vessels and cause pulmo- as the radiopharmaceutical is the in the event of oxidant formation by types [4]. The most commonly used in daily nary hypertension, while smaller particles result of the radiolabelled ligand. radiolysis. Examples are ascorbic acid routine at nuclear medicine departments may be retained by the reticuloendothe- • Reductant: For practical reasons (wa- and gentisic acid. Buffers are also often are discussed below, together with a lial system. ter solubility, stability, low toxicity used since radiochemical purity and few examples of the target-specific 99mTc Most radiopharmaceuticals are pre- and effectiveness at room tempera- biodistribution are pH dependent. Sol- radiopharmaceuticals in clinical use. A pared using lyophilised kits since they ture), stannous salts (most commonly ubilising agents are used to increase summary of their kit composition and considerably facilitate the radiopharma- stannous chloride) are the preferred the solubility in aqueous solutions labelling procedures is given in Table 1. cy’s practice. A kit is a prepacked set of reductants in kit formulations. The of highly lipophilic 99mTc complexes Other radiopharmaceuticals, with isotopes sterile reagents of guaranteed pharma- reductant influences the oxidation such as 99mTc-MIBI. Surfactants may such as indium-111 (111In) and iodine-123 ceutical quality designed for the easy state of 99mTc and, if a mixture of com- also be useful to prevent particle ag- (123I), are also briefly described [1–4]. preparation of a specific radiopharma- plexes is formed, the proportion of gregation. Additives, such as gelatine,

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Labelling Radiopharmaceutical Clinical indication Pharmaceutical ingredient Other ingredientes / excipients (Activity, volume, incubation) Shelf life after labelling RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE

Stannous chloride dehydrate, glucose Lymphoscintigraphy and Sen- 0.18 – 5.55 GBq 6 h, 2 – 25 ºC anhydrous, poloxamer 238, 99mTc-Colloids (e.g. Albumin tinel imaging , Human albumin colloidal nanocolloids) Bone marrow and inflammation particles Na 99mTcO , 1-5 ml, Invert Shake before withdraw- sodium phosphate dibasic, anhydrous, 4 carefully, 5 - 10 min ing a dose imaging sodium phytate, anhydrous Vial:, Edetate disodium, Gelatine; Sy- 99m Up to 18.5 GBq Na TcO4, ringe A: 1.5 ml of 0.148 N hydrochloric 1-3 ml, swirl; Lymphoscintigraphy and bone acid solution; 99mTc-Colloids (e.g. sulphur colloids) marrow imaging; Gastroesopha- Sodium thiosulfate anhydrous Add syringe A, boiling water, 6 h, 15 - 30 ºC geal reflux Syringe B: 1.5 mL aqueous solution of 5 min, cool 3 min; sodium biphosphate anhydrous and sodium hydroxide. Add syringe B and swirl Dynamic renal scintigraphy; Stannous chloride dihydrate, gentisic Up to 11.1 GBq Na99mTcO , trisodium diethylene- 4 99mTc-DTPA Measurement of glomerular acid and sodium chloride 2-10 ml, 15 -30 min at 15 8 h, 25ºC triamine pentaacetate filtration rate -25ºC Stannous chloride dihydrate Functional and renal scintigra- (Suc- Up to 3.7 GBq Na99mTcO , 5 99mTc-DMSA 4 5 h, above 25ºC phy cimer) inositol, ascorbic acid, sodium hydrox- ml (1 min shake),15 min ide Vial A: Stannous chloride dihydrate, disodium edetate, manitol, hydrochlo- N,N’-1,2-ethylenediy(bis-L- Cerebral perfusion Imaging; ric acid 3.7 GBq Na99mTcO , 2 ml cysteine diethyl ester 4 99mTc-ECD into Vial B + 1 ml Vial A, 30 8 h, ≤25 ºC Vial B: disodium phosphate heptahy- min, r.t. (Bicisate dihydrochloride) drate, sodium dihydrogen phosphate monohydrate,

99m Tc-HMDP Hydroxymethylenediphos- Stannous chloride dihydrate, ascorbic Up to 11.1 GBq Na99mTcO , 2 Bone imaging 4 8 h, 2 – 8 ºC phonic acid (Oxidronic acid) acid, sodium chloride – 10 ml (2 min swirl), 15 min

99m Stannous chloride dihydrate, sodium 0.37 – 2.0 GBq Na TcO4, 5 Cerebral perfusion Imaging; ml, 10 sec 30 min (without stabilizer) [(RR,SS)-4.8-diaza-3,6,6,9-tetra- chloride + Methylene blue sodium 99mTc-HMPAO Radiolabeling of autologous methylundecane-2,10-dione phosphates/sodium chloride (Stabilizer) Or Or leukocytes (preparation without bisoxime], (Exametazime) stabilizer) Add 2 ml stabilizer within 4 h (with stabilizer) 2 min

99m Tc-MAA Macroaggregates of human Stannous chloride dihydrate, human 2,22 GBq Na99mTcO maxi- Pulmonary perfusion imaging 4 6 -8 h, 2 – 8 ºC albumin albumin, sodium chloride mum, 5 – 10 ml, 15 min, r.t.

Table 1: Information regarding the composition and preparation of most commonly used radiopharmaceuticals.

76 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 77 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 6 CHAPTER 6

Radiopharmaceutical Clinical indication Pharmaceutical ingredient Other ingredientes / excipients Labelling Shelf life after labelling RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE (Activity, volume, incubation) RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE

Mercaptoacetyl triglycine Stannous chloride dihydrate, sodium 99m Tc-MAG3 Functional and renal scintigra- (R,R)-tartrate dihydrate, sodium hydroxi- Up to 2.5 GBq Na99mTcO , 2 (Mertiatide) 4 6 h phy de, hydrochloric acid ml, 15 min (no heating)

99m Tc-MDP Methylenediphosphonic acid stannous chloride dihydrate, Up to 11.1 GBq Na99mTcO , 2 Bone imaging 4 6 h, ≤25 ºC – 8 ml (1 min swirl), 1-2 min (Medronic acid) ascorbic acid (2,2’-[[2-[(3-Bromo-2,4,6-trime- 99m thylphenyl)-amino]-2-oxoethyl] Tc-Mebrofenin Stannous fluoride dihydrate, methylpa- Up to 3.7 GBq Na99mTcO , 1 – Hepatobiliary imaging agent imino] bisacetic acid) 4 18 h, 20 – 25ºC raben, propylparaben 5 ml, 15 min (Mebrofenin) Sodium citrate dihydrate, 0.92 – 5.55 GBq Na99mTcO , 99m 4 Tc-MIBI 2-methoxyisobutylisonitrile L-cysteine hydrochloride monohydrate, 1-3 ml, Vigorous shaking, 10 Myocardial perfusion imaging 6 h, 15 – 25ºC (MIBI) mannitol, min in boiling water, cool 15 min r.t. stannous chloride dihydrate,

Vial I: Tricine, Stannous chloride dihy- 1 ml water into Vial I; Transfer Scintigraphy of primary and met- drate, manitol; 0.5 ml to Vial II + Up to 2.2 99mTc-Tektrotyd astatic neuroendocrine tumors HYNIC-[D-Phe1, Tyr3-Octreotide] GBq Na99mTcO 1 ml max- 6 h, ≤25 ºC Vial II: EDDA; disodium 4 bearing somatostatin receptors. phosphate dodecahydrate, sodium imum), 80ºC, 20 min, cool hydroxide 30 min

99m Stannous chloride dihydrate, disodium Tc-Tetrofosmin 1,2-bis[bis(2-ethoxyethyl)phos- Up to 8.8 GBq Na99mTcO , 4 – Myocardial perfusion imaging sulphosalicylate, sodium D-gluconate, 4 12 h, 2 -25ºC phino]ethane (Tetrofosmin) 188 ml (mix 10 sec), 15 min sodium hydrogen carbonate

Scintigraphy of primary and met- Pentetreotide (DTPA conjuga- Gentisic acid, trisodium citrate, anhy- Transfer 111In chloride into ted Octreotide), drous, citric acid anhydrous, 111In-Octreotide astatic neuroendocrine tumors reaction vial.Gently swirl, 30 6 h, ≤25 ºC bearing somatostatin receptors. inositol min, ≤25 ºC

Table 1: Information regarding the composition and preparation of most commonly used radiopharmaceuticals.

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RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE 99m RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE 99mTc-diphosphonates that contains two tridentate IDA ligands Tc-DMSA Upon heating at 100°C, the benzoyl 99m 99mTc-labelled diphosphonate com­ coordinated to the metal. Tc can form different complexes with protecting group is released and the plexes are routinely used for bone Like other IDA derivatives, 99mTc- DMSA (meso-2,3-dimercaptosuccinic acid) coordinating thiol (SH) group becomes imaging, methylene diphosphonic acid mebrofenin is rapidly extracted from depending on the labelling conditions (e.g. available to coordinate the [TcV=O]3+ 99m - (MDP; = medronic acid) and blood into bile by active transport via the pH, concentration of TcO4 , Sn(II)/Sn(IV) core. More recently, a new formulation hydroxymethylene diphosphonic acid anionic site on the hepatocyte membrane; ratio, oxygen concentration and incuba- was introduced containing unprotected (HMDP, trivial name = oxidronic acid) this is the same site as is used for transport tion time). MAG3 that allows labelling at room tem- being the most common ones. of bilirubin, and 99mTc-mebrofenin is The renal imaging agent is obtained at perature. For both formulations, the la- 99mTc-MDP and 99mTc-HMDP correspond therefore useful for the assessment of low pH (pH 2–3) by labelling DMSA kits. It is belling involves a transchelation reaction to a mixture of technetium complexes hepatobiliary function. 99mTc-mebrofenin a Tc(III) complex with a proposed structure between [99mTcV-tartrate] and the incom-

whose composition depends strongly is cleared through the hepatobiliary (Tc(III)(DMSA)2) that involves the coordina- ing MAG3 ligand. on the kit formulation and labelling system but elevated serum bilirubin levels tion of two DMSA ligands to each Tc atom. 99mTc-MAG3 is highly bound to plasma 99m conditions. The molecular structures of increase its renal excretion. After intravenous administration, Tc-DM- proteins following intravenous injection.

these complexes is not fully established SA (Tc(III)(DMSA)2) accumulates slowly in However, the protein binding is reversible but it is considered that they must consist 99mTc-DTPA the renal cortex, primarily in the cells of the and the radiotracer is rapidly excreted of Tc(III) and Tc(IV) species. The bone 99mTc-DTPA was the first99m Tc radiophar- proximal tubule. It is indicated for kidney by the kidneys, in its intact form and uptake of 99mTc-diphosphonates is held to maceutical for renal imaging. The chemi- imaging for the evaluation of renal paren- primarily via active tubular secretion; it is result from chemisorption processes at the cal structure of 99mTc-DTPA has not been chymal disorders. However, if the DMSA therefore of value for the assessment of bone surface. There is increased uptake in fully determined but it is generally consid- labelling is performed at higher pH, ste- renal function. 99m areas of greater surface area associated ered that it corresponds to a Tc(IV) com- reoisomeric Tc(V) complexes are formed 99m with increased bone metabolism (e.g. plex with the metal coordinated by three (Tc(V)(DMSA)2), having a Tc=O core coordi- Tc-HMPAO fracture, infection and tumour). atoms and three oxygen atoms nated by four thiolate groups of two DMSA 99mTc-HMPAO was the first approved from the DTPA ligand. ligands, which have been found to localise 99mTc radiopharmaceutical for brain imag- 99mTc-mebrofenin 99mTc-DTPA undergoes rapid blood in medullary thyroid carcinoma. ing. HMPAO ([4,8-diaza-3,6,6,9-tetrameth- 99mTc complexes with derivatives by glomerular filtration and ylundecane-2,10-dione bisoxime; trivial of iminodiacetic acid (IDA) are useful is excreted unchanged into the urine. 99mTc-MAG3 name = exametazime) exists in two di- as hepatobiliary agents. Among the It is used to assess kidney function in a 99mTc-MAG3 is a hydrophilic and an- astereomeric forms, D,L- and meso-, and developed IDA derivatives, mebrofenin variety of conditions and to measure the ionic 99mTc(V) oxocomplex stabilised acts as a tetradentate ligand that forms (2,2’-[[2-[(3-bromo-2,4,6-trimethylphenyl)-­ glomerular filtration rate. A variable but by a tetradentate MAG3 ligand, co­ neutral and lipophilic Tc(V) oxocomplex- amino]-2-oxoethyl]imino] bisacetic low percentage of 99mTc-DTPA binds to ordinated through one sulphur atom es. The kit contains the D,L-racemate of acid) is the most commonly used in the serum proteins, and the glomerular and three nitrogen atoms. The original HMPAO because its Tc(V) oxocomplex nuclear medicine. Most probably, 99mTc- filtration rate is consequently lower than kit formulation for preparing 99mTc-MAG3 has a better brain retention compared mebrofenin corresponds to a mono­ when using standard insulin clearance. contains an S-benzoyl protected mer- with the congener complex obtained for anionic and lipophilic 99mTc(III) complex captoacetyltriglycine ligand (betiatide). the meso form of HMPAO. The Tc(V) com-

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RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE plex with D,L-HMPAO is unstable in aque- in aqueous medium. The 99mTc-coordina- proportion to myocardial blood flow and the cellular and mitochondrial mem- RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE ous solution due to the conversion of the tion of the ECD backbone is quite stable. without involvement of the Na,K-ATPase branes. However, unlike99mTc-MIBI, a sig- primary lipophilic complex to a secondary However, the presence of two ester func- membrane pump. Uptake is associated nificant part of 99mTc-tetrofosmin is bound hydrophilic complex, which is enhanced tionalities makes it labile to enzymatic hy- with intact cellular and mitochondrial in the intracellular cytosol of myocytes by the presence of reducing agents. drolysis in vivo. membrane potentials, with a strong and is not located in the mitochondria. The shelf-life of the reconstituted The ECD ligand exists as the L,L and accumulation in myocyte mitochondria. HMPAO kit without addition of a stabiliser D,D isomers. The 99mTc(V) complexes of The retention remains virtually 99mTc-MAA is 30 min, as the preparation shows a both isomers show brain uptake but unchanged after the time of injection. 99mTc-MAA, macroaggregated albumin radiochemical purity lower than 80% after only the L,L isomer is retained in the 99mTc-MIBI is used to assess myocardial labelled with 99mTc, is primarily used this time. After labelling, the addition of brain. As a lipophilic complex, 99mTc-ECD perfusion in ischaemia and infarction for perfusion lung imaging. The MAA

cobaltous chloride (CoCl2) extends the localises in the brain by passive diffusion conditions. particles range from 10 to 90 µm in size 99m shelf-life of Tc-HMPAO to 4 h. CoCl2 of its unionised form through the blood- and are formed by denaturation of the stabilises the 99mTc-HMPAO preparation brain barrier. Slow hydrolysis of the ester 99mTc-tetrofosmin protein when stannous chloride and HSA by oxidizing the excess of Sn(II) and by groups in blood and its rapid hydrolysis 99mTc-tetrofosmin (tetrofosmin = are heated under controlled conditions. acting as a scavenger. 99mTc-HMPAO in brain tissue lead to the formation of 1,2-bis[bis(2-ethoxyethyl)phosphino] The nature of the 99mTc binding to MAA has can also be applied in the labelling of more hydrophilic and polar metabolites ethane) is a lipophilic and cationic not been fully elucidated in terms of the autologous leukocytes. For this purpose, (carboxylic acid derivatives), which compound that corresponds to a Tc(V) type of complexation and oxidation state 99m 99m 99m + only the non-stabilised Tc-HMPAO can explains the brain retention of Tc-ECD. dioxocomplex ([ Tc-(tetrofosmin)2O2] ) of technetium. However, it is generally be used. It is generally considered that containing two bidentate ether considered that the Sn(II) reduces the brain uptake of 99mTc-HMPAO is due to 99mTc-MIBI functionalised diphosphine ligands. disulphide bonds in the protein and the the primary lipophilic complex and that 99mTc-MIBI (MIBI = 2-methoxyisobutyli- Unlike 99mTc-MIBI, the preparation of 99mTc- reduced technetium is coordinated by brain retention is due to its intracellular sonitrile) is a lipophilic and cationic 99mTc(I) tetrofosmin does not require heating and the formed SH groups. conversion to the non-diffusible complex, showing the Tc atom coordinat- involves a transchelation reaction with The lung localisation of 99mTc-MAA secondary hydrophilic complex. ed by six MIBI ligands. In the kit, MIBI is gluconate as the transfer ligand, which involves the microembolisation (i.e. incorporated in the form of a Cu(I) com- avoids the formation of low-valent Tc physical trapping) of the particles in 99mTc-ECD plex to mitigate its toxicity and facilitate complexes [e.g. Tc(III)] that could arise capillaries and precapillary arterioles. The 99mTc-ECD (ECD = N,N’-1,2-ethylenedi- lyophilisation, since MIBI alone is a volatile due to the reducing properties of the diameter of capillaries and precapillary yl(bis-L-cysteine diethyl ester) is a neutral liquid. The labelling is performed at 100°C tetrofosmin ligand. arterioles is about 10 µm and 20–30 and lipophilic Tc(V) oxocomplex suitable to promote the reduction from Tc(VII) to Similar to 99mTc-MIBI, 99mTc-tetrofosmin µm, respectively. 99mTc-MAA particles for brain perfusion imaging. The Tc=O3+ Tc(I) and facilitate the release of MIBI from is taken up into the heart in proportion are slighter larger and, when injected core is coordinated by two nitrogen at- its Cu(II) complex to coordinate to Tc(I). to myocardial blood flow without redis- intravenously, the first capillary beds oms and two sulphur atoms from the After intravenous injection, 99mTc-MIBI is tribution. 99mTc-tetrofosmin undergoes a encountered are the lungs. No particles tetradentate and trianionic ECD ligand, taken up into the heart by passive diffusion faster hepatic clearance comparative to larger than 150 µm should be present to which confers a high stability to 99mTc-ECD through the myocyte membranes, in 99mTc-MIBI. Its uptake by the myocytes oc- avoid lung embolism. curs by potential-driven diffusion across

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RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE 99mTc-albumin colloid 99mTc-sulphur colloid 99mTc-Tektrotyd reotide) has been in clinical use since the RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE This radiopharmaceutical corresponds 99mTc-sulphur colloid (99mTc-SC) is a This target-specific radiopharmaceuti- 1990s and was the first radiopharmaceu- to HSA microcolloid (also called colloidal dispersion of sulphur particles cal corresponds to the mixed-ligand com- tical to be approved for peptide receptor nanocolloid) labelled with 99mTc. It contains labelled with 99mTc. It is the only technetium plex 99mTc-EDDA/HYNIC-Tyr3-octreotide, imaging. 111In-pentetreotide contains the very small particles: the mean size of the radiopharmaceutical in clinical use in carrying a cyclic bioactive peptide (oct- biologically active ring of octreotide and particles is 0.03 µm and almost 95% are nuclear medicine that contains 99mTc in reotide derivative) that recognises some a DTPA unit that is covalently bound to smaller than 0.08 µm. The preparation of the non-reduced Tc(VII) oxidation state. of the somatostatin (sst) receptors, par- the D- group. 111In-pentet- 99mTc-albumin colloid involves the initial Technetium appears in this oxidation state ticularly subtype 2 and, to a lesser extent, reotide specifically binds to sst receptors, reduction of Tc(VII) to a lower oxidation due to the formation of insoluble and subtypes 3 and 5. with particular affinity to subtypes 2 and state with binding of the reduced Tc to quite stable technetium heptasulphide, 99mTc-Tektrotyd contains [D-Phe1,Tyr3]- 5. 99m 111 99m albumin microcolloid, most probably Tc2S7. The formation of Tc-SC involves octreotide (TOC) as the sst-binding In-pentetreotide, like Tc-Tektrotyd, through coordination by the protein SH the following major steps: (1) upon peptide and hydrazinonicotinic is used for scintigraphic localisation groups, as mentioned above for 99mTc- boiling in acidic conditions, there is acid (HYNIC) as a 99mTc coordinating of primary and metastatic NETs that MAA. hydrolysis of thiosulphate with release moiety. Furthermore, it is stabilised by bear sst receptors. In the past few After intravenous injection, 99mTc- of elemental sulphur, which aggregates, EDDA (ethylenediamino-N,N'-diacetic years, however, its use has started to albumin colloid undergoes rapid forming particles ranging in size from 0.1 acid), which acts as a co-ligand and be replaced by gallium-68-labelled 99m 99m blood clearance upon phagocytosis by to 1.0 μm; (2) Tc2S7 is formed during the coordinates to Tc following a tricine/ somatostatin analogues, which provide reticuloendothelial cells in liver, spleen reaction and becomes incorporated into EDDA exchange reaction. The molecular higher sensitivity and resolution using or bone marrow. After subcutaneous the sulphur particles. The kit composition structure of 99mTc-EDDA/HYNIC-Tyr3- PET imaging. injection into connective tissue, 30%–40% includes gelatine, which controls particle octreotide has not been fully assessed. of the 99mTc-albumin colloid particles are size and aggregation by forming a Nevertheless, it is generally accepted that 123/131I-MIBG filtered into lymphatic capillaries, are negatively charged protein coat on the it contains 99mTc(V) coordinated by one Metaiodobenzylguanidine (MIBG) is a then transported along the lymphatic particles, causing them to repel each HYNIC moiety and two EDDA ligands. noradrenaline analogue that enters neu- vessels to regional lymph nodes and main other. EDTA is also present to chelate any 99mTc-Tektrotyd is indicated for the roendocrine cells by an active uptake 3+ 99m - lymphatic vessels, and are finally trapped Al ion that may be present in the TcO4 detection of pathological lesions in mechanism via the transport- in the reticular cells of functioning lymph eluate and avoid its flocculation, which which sst are overexpressed, namely er and is stored in the neurosecretory nodes. 99mTc-albumin colloid is useful in would lead to accumulation of excessively neuroendocrine tumours (NETs). In granules, which results in specific accu- lymphoscintigraphy to demonstrate the large particles in the lungs. NETs, sst receptor imaging is useful for mulation in tissues of neuroendocrine or- integrity of the lymphatic system and 99mTc-sulphur colloid has different primary diagnosis, staging of the disease, igin. MIBG can be labelled with 123I or 131I. to differentiate venous from lymphatic uses in nuclear medicine, such as liver/ selection of patients for targeted therapy 123I-MIBG is preferred for diagnostic proce- obstruction, as well as for preoperative spleen imaging and bone marrow and monitoring of its efficacy. dures due to a more favourable dosime- imaging and intraoperative detection studies. Another common application is try. However, 131I-MIBG might be preferred of sentinel lymph nodes in several in lymphoscintigraphy to identify sentinel 111In-pentetreotide to estimate tumour uptake and retention, . lymph nodes in patients. 111In-pentetreotide ([111In-DTPA0]-oct- within MIBG therapy planning and prior

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RADIOCHEMICAL PURITY RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE to the administration of therapeutic doses neurons. In healthy humans, the binding Radiochemical purity (RCP) is defined conate in 99mTc-tetrofosmin and 99mTc-tar- RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE of 131I-MIBG. of 123I- to DAT allows the as the proportion, expressed as a per- trate in 99mTc-MAG3). 123/131I-MIBG can be obtained “ready visualisation of the striata as two “half- centage, of the total radioactivity in the To assess the RCP, some form of phys- for use” and with a radiochemical purity moon”-shaped hot spots on SPECT radiopharmaceutical that is associated icochemical separation technique must greater than 95% at expiry, as either “car- images. However, loss of the nigrostriatal with the desired radiolabelled chemical be used to separate the various radio- rier-added” or “non-carrier-added” (n.c.a.) dopaminergic neurons results in loss of species. For most diagnostic radiophar- chemical species prior to the quantifi- products. 123/131I-MIBG is used to detect the DAT associated with those neurons maceuticals, a RCP above 95% is desirable cation of radioactivity and subsequent and treat tumours of neuroendocrine ori- and absence of those hot spots. since the radiochemical impurities have calculation of their proportion. Numerous gin, particularly those of neuroectodermal a different biodistribution that will affect methodologies can be employed, includ- origin (phaeochromocytomas, paragan- the quality of the image and consequent- ing thin-layer chromatography (ITLC), pa- and ). In addition, QUALITY CONTROL OF ly delay accurate diagnosis. However, for a per chromatography (PC), gel permeation it can be useful for the study of disorders RADIOPHARMACEUTICALS few radiopharmaceuticals such a level of chromatography, high-performance of sympathetic innervation, for example in Quality control procedures are essential purity is not achievable (e.g. 99mTc-HMPAO: liquid chromatography (HPLC) and gel ischaemic and non-ischaemic cardiomy- to ensure the quality of any radiopharma- RCP >80%). electrophoresis. The RCP analysis must opathy. ceutical. Many of them are performed by Radiochemical impurities may arise be quick, accurate, based on relatively manufacturers, but the final preparation of from an incomplete radiolabelling reac- easy procedures and economical to gain 123I-ioflupane radiopharmaceuticals formulated as kits, tion or decomposition due to any factor the maximum amount of information in 123I-ioflupane (methyl (1R,2S,3S,5S)-8- the dispensing of individual doses and (e.g. chemical impurities, temperature or a minimum amount of time. Planar chro- (3-fluoropropyl)-3-[4-(¹²³I)iodophenyl]-8- the radiolabelling of patient’s autologous pH, , oxidizing or reducing agents). matography that includes PC and ITLC is azabicyclo[3.2.1]octane-2-carboxylate) samples are accomplished at the radio- As regards conventional 99mTc radio- the separation method universally em- is a analogue that binds to the pharmacy and the ultimate responsibility pharmaceuticals, the three types of radio- ployed in RCP determination, although transporter (DAT). Its structure lies with the radiopharmacist. Thus, quick chemical species that can be determined solid phase extraction separation meth- contains a fluoropropyl group that and discriminative tests should be applied are: (1) 99mTc ligand of interest (desirable ods based on cartridges are coming into enhances its selectivity towards the DAT to the dispensed radiopharmaceuticals radiochemical form) and the most com- use. over other neurotransmitter transporters. before release [3, 5]. mon radiochemical impurities, (2) free 123 99m 99m - I-ioflupane is commercially available Quality control procedures include the Tc pertechnetate ( TcO4 ) and (3) hy- Planar chromatography as a high-specific n.c.a. product ready assessment of radiochemical, radionuclid- drolysed-reduced 99mTc (insoluble 99mTc In planar chromatography, the solvent for use, and it is used for the differential ic and chemical purity as well as pharma- dioxide and/or 99mTc tin colloid). Never- (mobile phase) migrates up the strip, diagnosis between essential tremor and ceutical tests that comprise physicochem- theless, for certain radiopharmaceuticals moving the radiopharmaceutical solution degenerative parkinsonism. 123I-ioflupane ical and biological testing [5]. a fourth radiochemical impurity may also through the stationary medium (paper crosses the intact blood-brain barrier, be present, i.e. 99mTc labelled to other sec- or ITLC) and separating the various distributes to the brain and preferentially ondary compounds (e.g. 99mTc-HMPAO radiochemical species. Intrinsic properties binds to the DAT located predominantly may present radiolabelled hydrophilic of the radiopharmaceuticals, such as on the nigrostriatal dopaminergic species) or transfer ligands (e.g. 99mTc-glu- particle size, molecular mass and charge,

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Chromatographic R system f

RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE Radiopharma- RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE determine the distance migrated. Solvent travelled along the stationary phase ceutical Radiopharmaceu- Hydrolysed-re- 99m - Other RC 99m TcO (Solid phase / Mobile tical duced Tc 4 Impurities polarity also influences the solubility by each radiochemical species to the phase) 99mTc-Colloids (e.g. Whatman Nº1 or of each radiochemical species. Thus, distance travelled by the solvent front. Albumin nanocol- TLC-SA / metanol:water 0.0 (>95%) - 0.7 – 1.0 - solvent must be selected on the basis of The fraction of activity detected at loids) 85:15, v/v 99m Tc-Colloids (e.g. Whatman Nº1 or ITLC-SG 0.0 - 0.9 – 1.0 - its ability to separate the radiochemical each Rf value allows determination of sulphur colloids) / or saline 99m forms on each stationary phase. The most the RCP. For many conventional Tc ITLC-SG/ Saline 0.9 - 1.0 0.0 0.9 - 1.0 99mTc-DTPA - commonly used solvents are: 0.9% saline, radiopharmaceuticals (see typical Rf ITLC-SG / MEK 0.0 0.0 0.9 - 1.0 water, methyl ethyl ketone (MEK), acetone values in Table 2), the RCP analysis usually 99mTc-DMSA Whatman Nº1 or ITLC-SG 0.0 (> 95%) 0.0 0.0 (≤ 2%) - and . requires two chromatographic systems / MEK

99m BaKer Silica gel / Ethyla- Miniaturised chromatography proce­ Tc-ECD cetate 0.8 -1.0 (>94%) 0.0 0.0 – 0.2 - dures are the most extensively used. Whatman 17 / Saline; 1.0 0.0 1.0 The chromatographic strips or plates 99mTc-HMDP - Whatman 17 / meta- 0.0 0.0 0.4 – 1.0 are cut into small sizes and the line of nol:water 85:15, v/v application (origin) and the expected ITLC-SA / MEK 0.8 – 1.0 0.0 0.8 – 1.0 0.0 solvent front are marked (Figure 1). A few 99mTc-HMPAO ITLC-SA / Saline 0.0 0.0 0.8 – 1.0 0.0 Whatman Nº1/50% microlitres of the radiopharmaceutical 0.8 – 1.0 0.0 0.8 – 1.0 0.8 – 1.0 preparation is applied on the origin line. The chromatography strip is then 99mTc-MAA Whatman Nº 1 / Acetone 0.0 - 0.8 – 1.0 - developed in the appropriate solvent in 0.8 – 1.0 (≤ a chromatography chamber, ensuring ITLC-SA / MEK 0.0 0.0 5%) 99mTc-MAG3 - ITLC-SA / H O 0.8 – 1.0 0.0 – 0.1 (≤ 2%) that the spotting point is not immersed. 2 0.8 – 1.0

Following solvent migration along the strip Whatman Nº 1 or ITLC- SG/ Saline 0.9 - 1.0 0.0 0.9 - 1.0 to the solvent front, the strip is removed 99mTc-MDP - 0.0 0.0 0.9 - 1.0 from the chamber and allowed to dry. Figure 1: Typical chromatography strip ITLC-SG / MEK ITLC-SA / Saturated Radiochemical species are separated and showing the position of the origin and saline 0.0 0.0 0.9 – 1.0 99mTc-Mebrofenin - the strips can be either scanned with a solvent front (SF) lines Whatman Nº1 / 0.8 – 1.0 0.0 0.8 -1.0 radiochromatogram scanner or cut and glycol:water (1:1)

99m Baker Aluminium oxide counted for activity in a dose calibrator, to determine the percentage of each Tc-MIBI /Ethanol 0.8 – 1.0 0.0 0.6 – 0.7 - gamma counter or any other adequate radiochemical impurity: 99mTcO - and 4 ITLC-SG or ITLC-SA / MEK 0.0 0.0 0.8 – 1.0 equipment. hydrolysed-reduced 99mTc. In the case of 99mTc-Tektrotyd - ITLC-SA / Water: Acetic 0.8 -1.0 0.0 0.8 -1.0 Each radiochemical species migrates a a particulate radiopharmaceutical such acid (1:1) 99m 99m ITLC-SA / Aceton:Di- characteristic distance that is represented as a Tc-nanocolloid, neither the Tc 99mTc-Tetrofosmin chloromethane 65:35 0.4 -0.5 0.0 – 0.1 1.0 - 99m (v/v) as the relative front (Rf) value. The Rf colloids nor the hydrolysed-reduced Tc 1.0 111 is defined as the ratio of the distance migrate, so both remain at the origin. 111 ITLC-SG / 0.1 M Sodium ( In-hy- In-Octreotide citrate 0.0 - drophilic - impurities) Table 2: Recommended chromatographic systems for quality control of most commonly used radiopharmaceuticals

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RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE Thus, the only radiochemical impurity that from this step is also discarded. 99mTc: the radionuclidic purity of 99mTc can the generator eluate. A drop of the eluate RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE 99m - 99 can be separated is free TcO4 . 2. Loading the sample. be assessed by the Mo breakthrough test, is placed on a test paper and compared 99 99m - Table 2 presents some of the 3. Elution of the fractions. The first elution as Mo contamination on the TcO4 with a drop of the same volume of a stan- manufacturer-recommended step removes constituents that are can occur during a 99Mo/99mTc generator dard solution of Al3+. If the colour of the chromatographic systems for quality less strongly retained on the sorbent. elution. An approximate assay for 99Mo eluate drop is less intense than that of the control of conventional diagnostic Then, the analytes are eluted using a breakthrough can be performed using standard solution, the Al3+ concentration radiopharmaceuticals. Sometimes, it is solvent of higher eluting strength while a dose calibrator and a lead shield of is acceptable. convenient to develop alternative RCP more strongly adsorbed constituents around 6 mm thickness that attenuates testing procedures. In such cases, the are discarded with the sorbent. The the 140 keV gamma emission of 99mTc alternative procedure must be validated. elution of the fractions depends on while allowing the penetration of a OTHER ROUTINE QUALITY the radiopharmaceuticals and should portion (around 50%) of the higher CONTROL TESTS Solid phase extraction be carried out according to the energy gamma photons of 99Mo. Appearance Some manufacturers recommend manufacturer’s instructions. Comparison of the attenuated 99Mo with The colour and clarity of each radio- the use of reverse-phase Sep-Pak® a standard allows rapid estimation of the pharmaceutical preparation should be chromatography cartridges for the RCP contamination level. The activity of 99Mo checked. If a radiopharmaceutical is a true determination (e.g. 99mTc-MAG3 and 111In- RADIONUCLIDIC PURITY must not exceed 0.15 of the total 99mTc solution, no particulate matter should be octreotide). These Sep-Pak® cartridges Radionuclidic purity is the ratio, activity. present. 99mTc radiopharmaceutical prepa- work by solid-phase extraction, an expressed as a percentage, of the rations based on particles have varying extraction technique based on selective stated radionuclide activity to the total degrees of turbidity in appearance, rang- partitioning of one or more components radioactivity. Radionuclidic impurities CHEMICAL PURITY ing from white to milky. between two phases, one of which is a can have undesirable effects on the Chemical impurities are all non-radio­ solid sorbent and the other typically a patient’s overall radiation dose as well as active materials that can either affect Particle size and number liquid. on the image quality. Sometimes these radiolabelling or directly produce adverse To achieve the desired biodistribution, The Sep-Pak® C18 cartridge comprises impurities are radioisotopes of the same biological effects. radiopharmaceuticals formulated as a solid, non-polar sorbent that enables element as the desired radionuclide In 99Mo /99mTc generators, alumina oxide solutions or suspensions of particles must

separation of the various radiochemical and cannot be removed, or they may (Al2O3) is used as the column material to have the proper particle size and number species that may either adsorb to the solid be radioisotopes of an entirely different which the 99Mo radioactivity in the form of for each clinical indication. The size of 99mTc- 2- material or remain in the liquid phase. element. The most accurate method to molybdate ion (MoO4 ) is bound. Alumina MAA particles can be determined using a RCP analysis using these chromatography determine radionuclidic impurities is the breakthrough results in the presence of light microscope and a haemocytometer. cartridges requires multiple steps: technique of gamma spectroscopy, which, significant quantities of aluminium ions The total number of particles can be 1. Preconditioning of the sorbent with the however, is not commonly available at the (Al3+) in 99mTc eluates, which can interfere estimated from the number of particles organic solvent used to load the sample. radiopharmacy. in the radiolabelling reactions. This impu- in one millilitre, determined by counting The eluate is discarded. Thereafter, an The radionuclidic purity test of particular rity can be measured by the aluminium the particles within the haemocytometer. equilibration step is performed with interest in radiopharmacy relates to the ion breakthrough test, a colorimetric test of a low-strength solvent and the eluate most popular diagnostic radionuclide,

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REFERENCES RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE pH RADIOPHARMACEUTICALS CONVENTIONAL NUCLEAR MEDICINE To ensure stability and integrity, all 1. Kowalsky RJ, Falen SW. Radiopharmaceuticals in nuclear pharmacy and nuclear medicine. 3rd radiopharmaceuticals must maintain the ed. Washington D.C.: American Pharmacists As- most appropriate pH. The pH range of sociation; 2017. most radiopharmaceuticals is 4–8. 2. Saha GB. Fundamentals of nuclear pharmacy. 7th ed. New York: Springer; 2010. 3. Sampson CB. Textbook of radiopharmacy: The- ory and practice. 3rd ed. Amsterdam: Gordon & Breach; 1999. 4. IAEA. Technetium-99m radiopharmaceuticals: Manufacture of kits. Technical reports series nº 466. 2008. 5. Zolle I. Technetium-99m pharmaceuticals: Preparation and quality control in nuclear med- icine. Vienna: Springer; 2007.

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PET RADIOPHARMACEUTICALS

by Lei Li Corrigan

94 EANM TECHNOLGIST’S GUIDE RADIOPHARMACY: AN UPDATE 7 CHAPTER 7 CHAPTER 7

INTRODUCTION PET RADIOPHARMACEUTICALSPET Positron emission tomography (PET) employs short half-life positron- important 18F-labelled tracers include [18F] brain injuries. Similar to 11C-labelled RADIOPHARMACEUTICALSPET 11 13 emitting isotopes, such as carbon-11 ( C; t1/2 = 20.4 min) and fluorine-18 FMISO for the measurement of tissue hy- amino acids, N-labelled amino acids 18 18 ( F; t1/2 = 109.7 min), for in vivo measurement of physiological processes. poxia and [ F]FLT for the measurement can be used for measurement of protein PET imaging has been widely used in both diagnostic medicine and of cellular proliferation (Fig. 2), both of synthesis; however, the shorter half-life 13 clinical pharmaceutical research. The major clinical applications of PET which are valuable diagnostic tools to of N (t1/2 = 9 min) poses a big challenge are in , and . The use of positron-emitting measure response to cancer treatment. to the production and availability of the isotopes in PET contrasts with single-photon emission computed radiotracers. tomography (SPECT), where labelling is performed using gamma- Small organic compounds with known 99m emitting isotopes such as technetium-99m ( Tc; t1/2 = 6.01 h) and biological activity as receptors to important 111 11 indium-111 ( In; t1/2 = 2.8 days). proteins are labelled with C for in vivo assessment of the protein activity. For example, (R)- and metomidate Radionuclides used in PET imaging emit are licensed as short-acting intravenous positrons upon decay. For 18F, the decay agents for the induction of general results in the formation of an oxygen-18 anaesthesia and sedation in humans or atom and a positively charged beta Figure 2: PET study of a brain animals. The primary pharmacological particle (or positron) along with a neutrino. tumour using [18F]FLT (from Price et al. [1]) effect of this group of chemicals is to The positron subsequently annihilates inhibit β-hydroxylase, a key enzyme in the with a nearby electron to produce two Carbon, oxygen and nitrogen are biosynthesis of cortisol and aldosterone gamma quanta departing approximately abundant in biologically active chemicals. in the adrenal cortex. [11C]Metomidate 180° apart (Fig. 1). A cylindrical detector Therefore, when these chemicals was developed as a PET ligand for the surrounding the imaging target collects are labelled with carbon-11 (11C), diagnosis of primary hyperaldosteronism the simultaneously emitted gamma Figure 1: Positron emission tomography oxygen-15 (15O) or nitrogen-13 (13N), and adrenocortical tumours. quanta pair. Computer-aided image the radiopharmaceuticals metabolise [11C](R)-PK11195 has been used in PET reconstruction of the data allows for the The most widely used and studied PET in exactly the same way as their non- scanning to visualise brain inflammation output of 3D images of the regions of tracer is [18F]FDG. This tracer allows in vivo radioactive analogues. For example, in patients with neuronal damage. interest. Because a pair of gamma quanta measurement of abnormal glucose me- 11C-labelled amino acids such as L-[11C] Increases in [11C](R)-PK11195 binding is detected in PET, compared with only tabolism, which is known to be a typical leucine and L-[11C] are have been reported in patients with one gamma quantum in SPECT, the spatial symptom in cancer patients. During the used to measure protein synthesis rate, , traumatic brain injury and chronic resolution of PET images is higher than past 20 years, many automatic synthe- which is linked to brain function, and neurodegenerative conditions including that of SPECT images. However, the cost sisers and kits have been developed for 15O-labelled water or oxygen provides Huntington’s disease and Parkinson’s of PET is significantly higher than that of the manufacture of [18F]FDG and other quick non-invasive measurement of disease. SPECT because of the cost of the cyclotron 18F-labelled tracers synthesised via nucle- oxygen metabolism, blood volume and Thioflavin T is the dye widely used to visu- and the automatic radiolabelling process. ophilic fluorination of 18[ F]fluoride. Other cerebral perfusion in patients with acute alise and quantify the presence of misfold-

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PET RADIOPHARMACEUTICALSPET ed protein aggregates called amyloid, RADIOPHARMACEUTICALSPET both in vitro and in vivo. Its radioactive analogue, [11C]PIB, is used in PET to im- age beta-amyloid plaques in neuronal tissue and hence plays a critical role in investigational studies of Alzheimer’s disease and other disorders (Fig. 3)

Figure 4: GE PETtrace 800 medical cyclotron

18 11 [ F]Fluoride or [ C]CO2 can subse- quently be introduced in an organic Figure 3: Imaging beta-amyloid plaques compound via a single- or multi-step with [11C]PIB in Down syndrome synthesis. This is the so-called radiola- (from Landt et al. [2]) belling process. For protection of the operator, the radiolabelling process Due to the short half-life of 18F, 11C, usually occurs in an automatic synthe- Figure 5: Above: GE FastLab2 synthesiser. 13N and 15O, a medical cyclotron is usu- siser via a programmed time sequence Below: Synthra RNPlus synthesiser ally built next to the production facili- (Figs. 5, 6). At the end of the radiolabel- ty. Radioisotopes generated from the ling process, the radiopharmaceutical cyclotron can then be immediately will be purified, formulated, sterilised via transferred to an automatic synthesiser membrane filtration and aseptically dis- for use in the labelling process (Fig. 4). pensed in a vial as final product. 18 Typically, when bombarding [ O]H2O Figure 7: Typical manufacturing process for with proton beams, the nuclear reaction PET tracers and process control in the cyclotron target produces [18F] fluoride in18 O-water. When bombard- Compared with 99mTc radiopharmaceuti- ing nitrogen with oxygen with proton cals used in SPECT scans, the whole “radio- beams, the nuclear reaction in the gas synthesis” process for PET tracers as shown 11 target produces [ C]CO2 as the starting Figure 6: Automatic dispenser for PET tracers in Figure 7 is very costly and time consum- point of the radiosynthesis procedure. ing. In addition, the availability of 18F and

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PET RADIOPHARMACEUTICALSPET 11C radiochemistry limits the numbers of velopment of suitable antibody-based REFERENCES RADIOPHARMACEUTICALSPET

radiotracers that may be used in clinical radiopharmaceuticals with a radioisotope 1. Price SJ, Fryer TD, Cleij MC, Dean AF, Joseph J, Sal- studies. In the United Kingdom, most PET half-life matching the pharmacokinetic vador R, et al. Imaging regional variation of cellular radiopharmaceuticals are unlicensed me- half-life of the labelled antibodies in vivo. proliferation in gliomas using 3’-deoxy-3’-[18F]fluo- dicinal products and are supplied under a Because antibodies have relatively slow rothymidine positron-emission tomography: an im- age-guided biopsy study. Clin Radiol 2009;64:52–63. and Healthcare Products Regu- , they often require a latory Agency “Specials” licence. Only [18F] number of days to reach their optimal 2. Landt J, D’Abrera JC, Holland AJ, Aigbirhio FI, Fryer FDG for injection is a licensed product. biodistribution within the body. The short TD, Canales R, et al. Using positron emission tomog- As discussed previously, compared with half-life positron-emitting radioisotopes, raphy and carbon 11-labeled to image brain fibrillar β-amyloid in adults with down 18 11 18 11 68 SPECT tracers, F- and C-labelled PET e.g. F, C and Ga, are consequently not syndrome: safety, acceptability, and feasibility. Arch tracers have the advantage of increased a suitable choice in this context. Zirconi- Neurol 2011;68:890–896. resolution but the disadvantages of um-89 (89Zr) is gaining attention in PET being costly and dependent on a clinical studies because its half-life is 78.4 cyclotron. Recently, gallium-68 (68Ga) h, which represents a good match to the has become an increasingly popular pharmacokinetic of antibodies. Moreover, choice of radionuclide for PET studies it irradiates a pair of relatively low-energy owing to its practical and economic gammas (395.5 keV) after positron decay advantages. 68Ga is a generator-eluted and is hence safer to handle 18F and 11C radionuclide with 89% decay by positron irradiate relatively high-energy gammas emission. The long half-life of its parent (512 keV)]. radionuclide, germanium-68 (270.8 days), Radiolabelling of 68Ga and 89Zr is per- allows use of the generator for up to one formed via chelators. For example, the year. 68Ga-labelled peptides, for example most popular chelator for Zr4+ is desferri- 68Ga-DOTATOC, 68Ga-DOTATATE and 68Ga- oxamine, which has three hydroxamate DOTANOC, have been recognised as groups for binding the Zr4+ and a primary a new group of radiopharmaceuticals amine group. The primary amine group showing fast target localisation and blood can be modified for conjunction to bio- clearance. molecules, such as peptides, proteins or In recent years, antibodies have been ex- antibodies. tensively studied as attractive candidates for cancer therapeutics and drug delivery agents owing to their exquisite specificity and binding affinity. For similar reasons, resources have been invested in the de-

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RADIO- PHARMACEUTICALS PETUSED IN THERAPY RADIOPHARMACEUTICALS

by Christelle Terwinghe, Christopheby Lei Li Corrigan M Deroose

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INTRODUCTION • The instrumentation has to be prop- RADIOPHARMACEUTICALS USED IN THERAPY During the past decade, there has been significant growth in therapeutic erly calibrated, with calibration factors ablate the post-surgical thyroid remnant RADIOPHARMACEUTICALS USED IN THERAPY nuclear medicine. Cancer cells can be killed by damaging their DNA, and for each specific radionuclide and in (normal thyroid tissue) and accumulate other subcellular components, using radiation emitted by radionuclides particular cases with calibration fac- within the malignant tumour cells, either accumulated inside or in the vicinity of the tumour cells. Targeted radio- tors specific to the different materials in an adjuvant setting or for treatment of nuclide therapy is typically a systemic treatment, with distribution of the used, e.g. container, vial and syringe. metastatic disease (activity varies from 1 radiopharmaceutical through the bloodstream and retention in tumour Instrumentation has to be maintained to 6 GBq). Na131I is typically administered via specific uptake mechanisms. The radiopharmaceutical delivers a toxic according to the manufacturer’s in- orally. It can be provided in liquid form, level of radiation to the tumour cells, while healthy tissue is irradiated to structions. in which case the prescribed activity has a much lesser extent. For targeted , radionuclides are • The working space has to be clean to be dispensed, but most commonly it chosen that emit radiation with a short path length and with a high en- and the procedure has to be per- is delivered in individual capsules. The ergy deposition along that path length; examples include beta particles, formed in a sterile manner, e.g. swab- activity has to be checked in an activity alpha particles and Auger electrons. In this chapter, the most commonly bing surfaces with ethanol and work- meter before administration to the patient. used therapeutic radiopharmaceuticals are described [1, 2]. ing in a laminar airflow unit. In addition to the standard radiation • The appearance of the product (co- protection measures, one has to take 177 From a logistic perspective, therapeutic tium-177 ( Lu) through the use of a lour, homogeneity etc.) has to be into account the fact that working with 131 radiopharmaceuticals can be categorised DOTA chelator checked and should meet the manu- I presents a potential radioactive according to the complexity of the facturer’s description. contamination hazard because of the preparation to be performed at the clinical Depending on the complexity of the volatility of iodine. Manipulation of • The radionuclide purity has to be site where administration to the patient is manipulations, a number of quality control solutions poses the greatest danger and checked by recording the gamma-ray to be performed: tests should be performed: should therefore always be performed and X-ray spectrum if no chromato- within a fume hood. Use of capsules is grams are available in the certificate 1. Radiopharmaceuticals delivered in an recommended to reduce the risk, but the • Upon receipt of the radiopharma- of analysis. individual dose that is entirely admin- ceutical, the package has to be con- capsules should still be preserved in well- 131 istered, e.g. sodium iodide-131 (Na I) trolled. closed containers in a fume hood or a well- capsules Sodium iodide-131 ventilated room [3]. • The included documentation has to 2. Radiopharmaceuticals which are In 1948, iodine-131 (131I) became the be checked, e.g. certificate of analysis “ready to use” but which require dis- first radiopharmaceutical to be used in and time of calibration. pensing of a specific amount of activ- humans for the treatment of benign RADIOIMMUNOTHERAPY ity for administration, e.g. radium-223 • The surface of the container and the conditions of the thyroid gland. 131I is used Radioimmunotherapy (RIT) is a targeted 223 vial has to be swabbed to verify that dichloride ( RaCl2) vials to irradiate thyroid tissues in order to treat radionuclide therapy using a radiolabelled 3. Radiopharmaceuticals that require a the surface is not contaminated. specific forms of (for with specificity for labelling procedure involving indirect • The expiry date and time must be this purpose a small amount of activity a tumour-associated antigen allowing di- radiolabelling of the vector molecule checked. is employed, less than 1 GBq) and some rect delivery of therapeutic radionuclides (for instance by use of a chelator), forms of thyroid goitre. It is also used in the to the tumour. RIT is currently used in the e.g. labelling of octreotate by lute- treatment of differentiated , treatment of non-Hodgkin where the administered activity will (NHL).

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RADIOPHARMACEUTICALS USED IN THERAPY The best-known RIT pharmaceutical which binds to CD37, a glycoprotein lator), labelled with various radionuclides, DOTATATE is the most commonly used RADIOPHARMACEUTICALS USED IN THERAPY is 90Y-ibritumomab tiuxetan, a murine expressed by B cells. Betalutin® is under such as 177Lu and 90Y, are used in the treat- radiopharmaceutical. A gallium-68 (68Ga) monoclonal antibody sold under the study for patients with relapsed B-cell NHL ment of neuroendocrine tumours. 177Lu labelled DOTA-peptide (-TATA/-TOC/- trade name Zevalin® (Spectrum Pharma- [5]. It is delivered in a ready-to-use formu- has a beta energy emission of 0.5 MeV NOC) PET scan (preferably), or if PET is not ceuticals, Irvine, US). It is directed at the lation, and the required activity has to be and a maximum tissue penetration of less available, scintigraphy with indium-111 human CD20 antigen, which is expressed withdrawn from the vial and checked in than 2 mm, which results in a high tumour pentetreotide or a technetium-99m (99mTc) on B-cell NHL [4]. The labelling proce- an activity meter before administration. dose and a steep gradient towards the derivative has to be performed prior to dure to obtain the radiopharmaceutical is surrounding healthy tissue. 90Y has a maxi- treatment to confirm good uptake of the shown in Figure 1. mum range of 12 mm and is somatostatin analogue in the tumour therefore more suitable for larger tumours, lesions. with a higher probability of low-uptake ar- 177Lu-DOTATATE is commercialised un- eas that can still be irradiated by adjacent der the name Lutathera® (Advanced Ac- high-uptake areas (the so-called cross-fire celerator Applications, Saint-Genis-Pouilly, effect). 177Lu is both a beta- and a gam- France) and is delivered ready-made. In ma-emitting isotope; the gamma emis- some centres the radiopharmaceutical is Figure1: Labelling procedure 90Y-ibritumomab sion allows the performance of imaging prepared in house. This radiopharmaceu- and calculations [6]. tical is registered in Europe by the Euro- The quality control consists of a small Theranostics Novel PRRT radiopharmaceuticals under pean Medicines Agency. A randomised drop deposition on an instant thin-layer Theranostics refers to a specific targeted development use -213 and actin- controlled study, the Netter-1 trial [9], has chromatography silica gel (ITLC-SG) therapy performed after a specific ium-225 (225Ac), which are alpha emitters demonstrated a profound effect on pro- paper. The ITLC-SG paper is placed in a diagnostic scan using the same vector [7, 8]. Alpha emitters have the advantage gression-free survival and quality of life developing chamber, filled with saline to molecule radiolabelled with different of causing a much higher number of dou- [10] in patients with progressive midgut determine the radiochemical purity. The radionuclides. ble-strand breaks in the tumour cell’s DNA neuroendocrine tumours. A strong effect radiolabelled antibody is retained at the compared with beta emitters. on overall survival has been suggested by origin and non-bound yttrium-90 (90Y) Peptide receptor radionuclide For the treatment of neuroendocrine an interim analysis, and the final analysis is will be chelated by DPTA and migrate therapy tumours, which very frequently show high awaited. with the solvent front. The strip can be Peptide receptor radionuclide thera- somatostatin receptor expression, 177Lu- scanned by an autoradiography system or py (PPRT) involves the administration of it can be cut and both halves counted in a radiopharmaceuticals that bind to the scintillation crystal. somatostatin receptor. A range of soma- A promising new RIT radiopharmaceu- tostatin analogues with bifunctional che- tical is 177Lu- satetraxetan (Beta- lators, such as DOTATOC, DOTATATE, and lutin®, Nordic Nanovector, Oslo, Norway), DOTANOC (where DOTA refers to the che-

Figure2: Labelling procedure 177Lu-DOTATATE

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RADIOPHARMACEUTICALS USED IN THERAPY The labelling can be performed semi- treatment of patients with prostate required activity has to be withdrawn and emits beta particles and gamma photons RADIOPHARMACEUTICALS USED IN THERAPY automatically or manually, depending on cancer after establishing high PSMA checked before administration. with a relatively short half-life (46 h) and the availability of a synthesis module at expression through a PET scan with a a relatively high dose deposit. 153Sm-EDT- the department. However, both methods gallium-68 or fluorine-18 18( F) labelled MP is available under the trade name require several steps, as shown in Figure 2. PSMA ligand. 177Lu-PSMA is one of the BONE-SEEKING RADIONUCLIDE Quadramet® (, Paris, France). Fast dilution of the product after labelling most promising radiopharmaceuticals for THERAPY Quadramet® is supplied frozen in a 10-ml is of great importance to avoid radiolysis use in radionuclide therapy. The labelling Bone-seeking radionuclide therapy has vial and has to be stored in the freezer. The owing to the small (<1 ml) volume of the and quality control are similar to those for been used for the palliation of pain caused vial contains 2–4 GBq in a concentration labelled peptide. 177Lu-DOTATATE. by bone metastases for decades, mostly of 1.3 GBq/ml on the reference date. After As with somatostatin analogues, in patients with prostate cancer and to a defrosting, the required activity has to be Additionally, some quality control tests radionuclides other than can lesser extent in those with . A dispensed (37 MBq/kg body weight). The have to be performed: be attached to the PSMA ligands. Very novel indication emerged after publication activity in the syringe has to be checked in • pH determination promising results have been shown with of the ALSYMPCA trial, where the alpha the activity meter. 225 223 • Radiochemical purity test by use of Ac attached to PSMA, with complete emitter RaCl2 was shown to prolong 223 high pressure liquid chromatogra- responses in patients refractory to all overall survival [12]. RaCl2 177 223 phy or ITLC standard and Lu-PSMA. Patient selection is performed by diag- Radium-223 dichloride ( RaCl2) is an • Radionuclide half-life determina- Other radionuclides that have been nostic 99mTc-methylene diphosphonate alpha emitter and has a natural affinity for tion studied in the preclinical setting include scintigraphy or 18F PET imaging examina- newly formed osteoid, the organic pre- • Bubble point test of the used ster- terbium-161 and scandium-47 [11]. tion shortly before planned treatment ad- cursor of bone tissue. It is the most recent ile filter ministration. addition to the radionuclide armamentari- • Sterility test by use of bacterial cul- 131I-mIBG Strontium-89, samarium-153, rheni- um for bone-seeking radionuclide therapy. ture media Iodine-131 metaiodobenzylguanidine um-186, rhenium-188 and phosphorus-32 The therapeutic regimen, validated by the • Pyrogenicity control by use of an (131I-mIBG) is used for the treatment of are radionuclides currently in clinical use randomised, controlled ALSYMPCA trial, endotoxin detection kit, e.g. lim- tumours arising from the neural crest, such in metastatic castration-resistant prostate consists of six intravenous injections (55 ulus amoebocyte lysate (LAL) test as neuroblastomas (a tumour typically cancer [13]. kBq/Kg body weight) every 4 weeks. 223 seen in children), and RaCl2 is delivered ready to use under phaeochromocytomas. The targeting of 153Sm-EDTMP the tradename Xofigo® ( Pharma- PSMA therapy (PRLT) the radiopharmaceutical is demonstrated Samarium-153 ethylene diamine te- ceuticals, Berlin, Germany). After calcula- Prostate-specific membrane antigen by a diagnostic scan with 123I-mIBG or a tramethylene phosphonate (153Sm-EDT- tion of the required activity, the volume (PSMA) is a protein overexpressed in the small amount of 131I-mIBG. MP) is used for palliation of in of the solution to be withdrawn is deter- vast majority of prostate . Several 131I-mIBG is shipped and delivered on patients with multiple painful osteoblas- mined. The activity in the syringe has to be radiopharmaceuticals using 177Lu attached dry ice and has to be stored in the freezer. tic skeletal metastases and has demon- checked by measuring the delivered vial to PSMA-binding vector molecules are Before injection the radiopharmaceutical strated efficacy in patients with prostate, before and after withdrawal of the solution used or are under investigation for the has to be defrosted and diluted. The breast and other primary cancers. 153Sm in the activity meter.

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SELECTIVE INTERNAL

RADIOPHARMACEUTICALS USED IN THERAPY 9. Navalkissoor S, Grossman A. Targeted alpha RADIOPHARMACEUTICALS USED IN THERAPY RADIATION THERAPY Disclosure statement: the work of particle therapy for neuroendocrine tumours: Selective internal radiation therapy (SIRT), SIRTEX Medical, Lane Cove, Australia), Christophe M Deroose is being partly The next generation of peptide receptor ra- also known as radio-embolisation, is 90Y-glass microspheres (TheraSphere®, supported by commercial organisations. dionuclide therapy. Neuroendocrinology used in patients with inoperable liver BTG, London, UK) and holmium-166 con- 2019;108:256–264. 10. Strosberg J, El-Haddad G, Wolin E, Hendifar A, tumours (primary tumours, hepatocellular taining microspheres (QuiremSpheres®, Yao J, Chasen B, et al. Phase 3 trial of 177Lu-do- carcinoma or ) or liver Terumo, Leuven, Belgium). Some of them REFERENCES tatate for midgut neuroendocrine tumors. N metastases from other tumours (colorectal are delivered by patient-specific ordered Engl J Med 2017;376:125–135. cancer, neuroendocrine tumours, breast activity and can be administered without 1. Yeong CH, Cheng MH, Ng KH. Therapeutic radio- 11. Strosberg J, Wolin E, Chasen B, Kulke M, Bush- nuclides in nuclear medicine: current and future nell D, Caplin M, et al. Health-related quality of cancer, ocular melanoma and others). manipulating the radiopharmaceutical. prospects. J Zhejiang Univ Sci B 2014;15:845– life in patients with progressive midgut neuro- The therapy consists in injecting For SIR-Spheres, the required activity has 863. endocrine tumors treated with 177Lu-dotatate radioactive microspheres directly into the to be dispensed from a bulk vial to the 2. Le D. Radiopharmaceuticals for therapy. J Nucl in the phase III NETTER-1 trial. J Clin Oncol Med 2017. May 25. pii: jnumed.117.196568. doi: 2018;36:2578-2584. hepatic artery after catheterisation under delivery V-vials. Prior to withdrawal, the 10.2967/jnumed.117.196568. [Epub ahead of 12. Muller C, Domnanich KA, Umbricht CA, van X-ray guidance. The uptake in the tumour required volume from the bulk vial has to print] der Meulen NP. Scandium and terbium radio- is typically higher than that in healthy liver be calculated and the spheres have to be 3. Robbins RJ, Schlumberger MJ. The evolving nuclides for radiotheranostics: current state of tissue because of preferential perfusion of mixed in suspension by slightly shaking role of (131)I for the treatment of differentiated development towards clinical application. Br J thyroid carcinoma. J Nucl Med 2005;46 Suppl Radiol 2018;91:20180074. tumour by the hepatic artery and normal them. The dispensed activity has to be 1:28S–37S. 13. Parker C, Nilsson S, Heinrich D, Helle SI, O’Sulli- liver tissue by the portal vein. determined by measuring the bulk vial 4. Papi S, Martano L, Garaboldi L, Rossi A, Cremone- van JM, Fossa SD, et al. Alpha emitter radium-223 For clinical use, three types of micro- before and after withdrawal. In both cases, si M, Grana CM, et al. Radiolabeling optimization and survival in metastatic prostate cancer. N sphere are available (all three are implant- with or without withdrawal, the activity and reduced staff for high- Engl J Med 2013;369:213–223. dose 90Y-ibritumomab tiuxetan (HD-Zevalin). 14. Nair VJ, Malone C, Moretto P, Lueng E, Malone able medical devices from a regulatory has to be checked before administration Nucl Med Biol 2010;37:85–93. S. Bone-seeking targeted radio-nuclide therapy point of view, and not radiopharmaceuti [14, 15] (Table 1). 5. Blakkisrud J, Holtedahl JE, Londalen A, Dahle J, (BT-RNT) in management of metastatic castra- cals): 90Y-resin microspheres (SIR-Spheres®; Bach-Gansmo T, Holte H, et al. Biodistribution tion-resistant prostate cancer (mCRPC): Shifting and dosimetry results from a phase 1 trial of from palliation to improving survival. J Nucl Med therapy with the antibody-radionuclide conju- Radiat Ther 2015;6:1–8. SIR-Spheres® TheraSphere® QuiremSpheres® gate 177Lu-lilotomab satetraxetan. J Nucl Med 15. Prince JF, van den Bosch M, Nijsen JFW, Smits 2018;59:704–710. MLJ, van den Hoven AF, Nikolakopoulos S, et al. 6. Bodei L, Mueller-Brand J, Baum RP, Pavel ME, Required manipulation Dispensing Measurement of the activity Measurement of the activity Efficacy of radioembolization with 166Ho-mi- Horsch D, O’Dorisio MS, et al. The joint IAEA, crospheres in salvage patients with liver metas- EANM, and SNMMI practical guidance on pep- tases: A phase 2 study. J Nucl Med 2018;59:582– Radionuclide Yttrium-90 Yttrium-90 Holmium-166 tide receptor radionuclide therapy (PRRNT) in 588. neuroendocrine tumours. Eur J Nucl Med Mol 16. Mosconi C, Cappelli A, Pettinato C, Golfieri R. Ra- Material Resin Glass Poly-L-lactic acid Imaging 2013;40:800–816. dioembolization with yttrium-90 microspheres 7. Kratochwil C, Giesel FL, Bruchertseifer F, Mier W, in : Role and perspec- Apostolidis C, Boll R, et al. 213Bi-DOTATOC recep- tives. World J Hepatol 2015;7:738–752. Mean diameter (µm) 32 25 30 tor-targeted alpha-radionuclide therapy induces remission in neuroendocrine tumours refractory Table 1: Overview of available microspheres for SIRT to beta radiation: a first-in-human experience. Eur J Nucl Med Mol Imaging 2014;41:2106–2119. 8.

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BLOOD LABELLING FOR NUCLEAR IMAGING

by Naseer Khan, Giorgio Testanera

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INTRODUCTION RADIOPHARMACEUTICALS BLOOD LABELLING FOR NUCLEAR IMAGING Blood cells can be radiolabelled with various radionuclides, including care needs to be exercised. One of the USED FOR CELL LABELLING BLOOD LABELLING FOR NUCLEAR IMAGING predominantly indium-111 (111In), technetium-99m (99mTc) and requirements is to have a clear physical The key radionuclides used in cell labelling chromium-51 (51Cr), for a variety of clinical applications. The radiolabelling barrier in place when handling different are shown in Table 1. The choice of radio- process is carried out either in vitro, as in the case of radiolabelled cells, and all syringes and test tubes must nuclide depends upon the characteristics leucocytes, or using an in vivo method, as in the case of radiolabelled be labelled with the patient’s name to of the radionuclide as well as the length of red cells. In vitro methods involve the initial isolation of blood cells, avoid possible cross-contamination. The the clinical study. The ligands labelled with radiolabelling with the suitable labelling agent and subsequent re- procedure is performed at room either 99mTc-99m or 111In form lipophilic injection of the labelled cells into the patient [1, 2]. temperature unless otherwise specified in complexes and are non-selective. There- the package insert for the radiopharma­ fore, it is paramount to isolate the cells Red blood cells (erythrocytes), white have sufficient stability in vivo as elution ceutical. The volume of blood collected required prior to labelling. This part of the blood cells (leucocytes) and platelets of radioactivity during the course of the may vary and is generally between 30 and process is the most time consuming. are all used in the labelling process. Red investigation could result in unnecessary 50 ml but this needs to be adjusted in blood cells are the most abundant cel- irradiation of the other organs and in proportion to body weight in paediatric Gamma lular elements. These cells are produced essence failure of the procedure. patients (Fig. 1). In the same way, the Half-life Radionuclide energy (t ) in the bone marrow. Haemoglobin, an activity in paediatric patients needs to be 1/2 (keV) important component of red blood cells, in proportion to the body weight. and other cellular proteins may contrib- REGULATORY REQUIREMENTS 99mTc 6 h 140 ute to the binding of radiolabels to the FOR BLOOD CELL LABELLING cells [1]. Leucocytes include granulocytes, The procedure should be carried out in a 111In 67.9 h 171, 245 monocytes and lymphocytes. Granulo- laminar flow hood or blood cell isolator as cytes migrate to the site of the infection defined by the local regulations. General 51Cr 27.7 days 320 and inflammation. The primary function care should be taken to protect both of these cells is to phagocytose and de- blood components and the individual Table 1: Radionuclides used for blood cell stroy bacteria, and this function is exploit- performing the procedure. As the labelled labelling ed during the imaging process for the blood cells are re-injected into the detection of the sites of infection. Plate- patient, strict adherence to aseptic lets are derived from megakaryocytes in technique is essential. All reagents and RADIOLABELLING OF WBCS the bone marrow and are non-nucleated glass/plasticware should be sterile and AND PLATELETS discs. protective clothing (gloves, face mask Non-selective, lipophilic 111In and 99mTc The ideal cell labelling agents will not and/or apron) must be worn during the complexes are used for radiolabelling of damage the cells. The agent used for manipulation of blood components. WBCs and platelets. labelling must be neutral and sufficiently Simultaneous labelling of blood cells lipophilic that it can cross the cell from more than one patient is membrane. Furthermore, the agent must discouraged, and if it is performed, special Figure 1: Example of blood collection

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BLOOD LABELLING FOR NUCLEAR IMAGING Clinical indications for labelled WBC 111In WBC labelling 99mTc-HMPAO WBC labelling BLOOD LABELLING FOR NUCLEAR IMAGING scintigraphy Indium-111 is supplied in high specific Technetium-99m has been extensively The main clinical indications for activity with no carrier added, as the used for radiolabelling of cells, and 99mTc- 99mTc-hexamethylpropylene amine oxime chloride in 0.04 mol/L hydrochloric acid. HMPAO has been developed as a cell (HMPAO)-labelled WBC and 111In-oxine-la- Oxine (8-hydroxyquinoline) is the ligand labelling agent (Fig. 4B). belled WBC scintigraphy are localization used for the 111In labelling of leucocytes of any occult site of infection and de- [4]. Oxine forms a 3:1 complex with indium termination of the extent of the process that is neutral and highly lipophilic (see [3–5]. Applicable disorders include: Fig. 4A below). This property of the ligand allows rapid diffusion of the complex • Osteomyelitis of the appendicular through the cell membrane. Once inside skeleton the cell, the indium complex completely • Infected joint and vascular pros- or partially dissociates, allowing indium Figure 4: A 111In-oxine complex; B 99Tc- thesis binding to the intracellular proteins. 111In- Figure 2: Centrifugation of blood sample to HMPAO complex • Diabetic foot oxine will also label the transferrin present remove plasma • in the plasma; therefore cells need to be presence of a relatively small amount • Postoperative abscesses washed thoroughly to remove plasma of stannous chloride. In addition, the • Lung during the labelling process (Figs. 2, 3). age and radioactive concentration of the • Endocarditis This complex gives a higher radiolabelling generator eluate can affect the formation • Neurological infections efficiency (80%–90%) as compared to the of the primary complex. The extent of • Infected central venous corresponding 99mTc complex. Therefore, degradation is higher with generator or other devices 111In-oxine-labelled WBCs are still widely eluate older than 2 h and with eluate from • Inflammatory bowel disease used in clinical settings for infection generator which has not been eluted (111In-oxine-labelled WBCs pre- imaging. The drawbacks of the complex within the last 24 h [1, 3, 6]. ferred) are those associated with the physical • Intra-abdominal infection properties of the radionuclide, i.e. the Clinical indications for 111In-labelled (111In-oxine-labelled WBCs pre- longer half-life and higher radiation platelet scintigraphy ferred) energy [1, 4]. The main clinical indication for 111In- • Kidney infections (111In-oxine-la- labelled platelet scintigraphy is idiopathic belled WBCs preferred) thrombocytopenic purpura (low platelet • AIDS count). Patients with this condition may have therapeutic indications for Figure 3: Separation of blood components splenectomy that need to be validated. following centrifugation The scan is then necessary to ensure

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MEASUREMENT OF RED CELL BLOOD LABELLING FOR NUCLEAR IMAGING that the site of platelet destruction is the conical test tube by removing the syringe MASS LABELLED WITH 51CR Clinical indications for red cell mass BLOOD LABELLING FOR NUCLEAR IMAGING spleen. For performance of the scan, it plunger and allowing the blood to flow Polycythaemia is suspected when measurements is fundamental that the patient’s platelet slowly down the side of the tube. haemoglobin and haematocrit are raised. The main clinical indication for red cell count is between 5000 and 90,000 per To obtain the platelet-rich plasma Routine laboratory screening does not labelling is to verify a clinical diagnosis of microlitre (5–90x109/L). A platelet count (PRP), the blood is then centrifuged. A differentiate true polycythaemia, i.e. polycythaemia vera or of less than 5000 may result in failure of slow centrifugation speed for a longer elevated red cell mass (RCM: the total [12]. the labelling procedure. If the platelet time, i.e. 180 g for 15 min, or a fast speed volume of red blood cells), from apparent, count is below 5000, the referrer may with a shorter time, i.e. 1000 g for 2 min, or pseudo-polycythaemia, i.e. reduced Labelling procedure for red cell mass suggest medical therapy to bolster the is preferred [7]. The PRP should contain plasma volume. Radiolabelled cells can and plasma volume studies platelet count [7]. 60% population of platelets with very be used to measure RCM. Plasma volume In all cases prior to 1993, the method few contaminating cells present. Once can be calculated from the haematocrit used was that recommended by the Inter- Procedure for 111In-labelled platelet they have been centrifuged, the cells are or measured independently using national Committee for Standardization in scintigProcedure for 111In-labelled washed with a plasma-free medium once. radiolabelled human serum albumin [8– . This method has been widely platelet scintigraphy The platelet pellet is resuspended gently 10]. Measurement of RCM is done using published and therefore will not be de- This procedure has been described into the buffer, forcing the solution over 51Cr-sodium chromate, and measurement scribed in detail. Briefly, it consists in label- in detail by Mathias and Welch [7]. the pellet several times with a pipette. The of plasma volume using radioiodine- ling erythrocytes with 51Cr to measure RCM The general procedure for preparing cells are virtually lifted into the solution. labelled human serum albumin as a and with radioiodine-labelled human se- platelets for radiolabelling is to carefully The process is shown in Figure 5: plasma label. There is evidence that rum albumin to measure plasma volume withdraw whole blood with the use of a protein with a molecular [13]. A 10-mL sample of venous blood is a large diameter needle, weight considerably greater than that of obtained and subsequently radiolabelled 51 ideally discarding the first albumin will give a smaller estimate of the with Cr Na2CrO4. Radiolabelled blood is millimetre since it will contain distribution space and probably a more re-injected and venous samples are ob- a large quantity of tissue accurate indication of the true plasma tained 15 and 30 min post injection. Radio- thromboplastin fibrinogen. volume. However, in practice no suitable activity is counted in the blood samples The whole blood should alternative preparations are available as and compared with known standards us- be drawn into a syringe yet. ing a gamma counter to establish plasma containing either acid citrate Not only is measurement of RCM es- and red cell volumes. The experimental or dextrose or 3.8% trisodium sential for the diagnosis of polycythaemia measured values are then compared with citrate. After withdrawal, the vera, but it is widely believed that mea- predicted values for height and weight of whole blood should be gently surement of RCM by the 51Cr labelling the patient. rotated to uniformly mix method is very accurate and that the RCM the anticoagulant with the is measured independently of the venous blood, and the blood is then Figure 5: Schematic of the radiolabelling of platelets (from [7], haematocrit. It is also widely believed that transferred to a polypropylene with permission) measurement of RCM must be done with 51Cr [8, 11].

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QUALITY CONTROLS FOR CELL BLOOD LABELLING FOR NUCLEAR IMAGING LABELLING REFERENCES BLOOD LABELLING FOR NUCLEAR IMAGING Acknowledgements. The authors would like to express For routine clinical use, visual inspection of 1. Danpure H, Osman S. Radiolabelling of blood 9. Spivak JL. Polycythemia vera: myths, mecha- the final product and determination of the their special thanks to the Radiopharmacy Depart- nisms, and management. Blood 2002;100:4272– ment at St. Bartholomew Hospital, London for their cells – theory. In: Sampson CB, ed. Textbook of labelling efficiency are usually considered radiopharmacy. Amsterdam: Breach Science 4290. help with pictures and procedures. 10. Silver RT, Chow W, Orazi A, Arles SP, Goldsmith sufficient. It is also fundamental to visually Publishers; 1994:69–74. 2. Costa D, Lui D, Ell PJ. White cells radiolabelled SJ. Evaluation of WHO criteria for diagnosis of assess the final product (Fig. 6) and to with 111In and 99Tcm – a study of relative sen- polycythemia vera: a prospective analysis. Blood double check the production worksheet sitivity and in vivo viability. Nucl Med Commun 2013;122:1881–1886. in the release project to ensure that all 1988;9:725–731. 11. Dworkin HJ, Premo M, Dees SJT. Comparison of red cell and whole blood volume as performed steps have been followed correctly and 3. de Vries EF, Roca M, Jamar F, Israel O, Signore AJ. Guidelines for the labelling of leucocytes with using both chromium-51-tagged red cells and that no expired reagents have been 99mTc-HMPAO. Eur J Nucl Med Mol Imaging iodine-125-tagged albumin and using I-131- used. In the implementation of the 2010;37:842–848. tagged albumin and extrapolated red cell vol- ume. Am J Med 2007;334:37–40. procedure, an accurate checklist needs to 4. Roca M, de Vries EFJ, Jamar F, Israel O, Signore 12. Alvarez-Larrán A, Ancochea A, Angona A, Pedro be provided and filled in by the operator. A. Guidelines for the labelling of leucocytes with (111)In-oxine. Inflammation/Infection C, García-Pallarols F, Martínez-Avilés L, et al. Red Microscopic inspection of clumping, the Taskgroup of the European Association of Nu- cell mass measurement in patients with clini- trypan blue exclusion viability test and the clear Medicine. Eur J Nucl Med Mol Imaging cally suspected diagnosis of polycythemia vera or essential thrombocythemia. Haematologica post-release sterility test may be used as 2010;37:835–841. 5. Signore A, Jamar F, Israel O, Buscombe J, Mar- 2012;97:1704–1707. additional quality controls [3]. tin-Comin J, Lazzeri E. Clinical indications, 13. Recommended methods for measurement of image acquisition and data interpretation for red-cell and plasma volume: International Com- white blood cells and anti-granulocyte mono- mittee for Standardization in Haematology. J clonal antibody scintigraphy: an EANM proce- Nucl Med 1980;21:793–800. dural guideline. Eur J Nucl Med Mol Imaging 2018;45:1816–1831. 6. Roca M, Martin-Comin J, Becker W, Bernardo-Fil- ho M, Gutfilen B, Moisan A, et al. A consensus protocol for white blood cells labelling with technetium-99m hexamethylpropylene amine oxime. Eur J Nucl Med 1998;25:797–799. 7. Mathias CJ, Welch MJ. Radiolabeling of platelets. Semin Nucl Med 1984;14:118–127. 8. Srivastava SC, Chervu LR. Radionuclide-labeled red blood cells: current status and future pros- pects. Semin Nucl Med 1984;14:68–82.

Figure 6: Visual assessment of the final product of 111In-WBC labelling

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GOOD MANUFACTURING PRACTICE FOR RADIO- PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT

by Kishor Solanki

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INTRODUCTION PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE Good manufacturing practice (GMP) is that part of quality assurance • Guidance on current good radiophar- play an important role in clinical practice (QA) which ensures that radiopharmaceuticals (RP), which are medicinal macy practice (cGRPP) for the small- in terms of guaranteeing the safety of products, are produced consistently and are fit for human administration. scale preparation of radiopharmaceu- patients. The patient must receive the correct radiopharmaceutical at the correct ticals (2010) [5] In essence, GMP is concerned with both radioactive dose with a high radiochemical purity. Radiopharmaceuticals production and robust QA/QC. Therefore, should be controlled to ensure compliance with quality standards, mostly • Guidelines on current good radio- the key topics covered in this chapter will set by the European Pharmacopoeia, and should be appropriate for the pharmacy practice (cGRPP) in the include: intended use. preparation of radiopharmaceuticals (2007) [6] • Control of preparation processes Radiopharmaceuticals are radioactive; exceeded when this product is prepared • Quality assurance and quality control they therefore have a short shelf life and are in hospitals. The radioactivity burden and The time between preparation of • Key personnel prepared close to patient use in a hospital product expiry after addition of radioactiv- radiopharmaceuticals, quality control • Control and ongoing validation of ‘hotlab’ or cyclotron. They are subject to ity are part of a manufacturer’s marketing (QC) and clinical use is very tight. At the premises and equipment European rules on radiation for medical authorisation and the manufacturer has international level, the Pharmaceutical • Essential documentation applications [1]. The main points to to provide related documented evidence Inspection Convention/Pharmaceutical • Safe and secure storage and distribu-

highlight are the importance of ensuring and justification. Incorrect preparation Inspection Co-operation Scheme (PIC/S) tion of radiopharmaceuticals the safety of personnel and the need for could result in poor quality product that guidelines aid in the harmonisation of • Good practices in relation to waste good aseptic techniques when preparing could compromise patient diagnosis. practices [7] and place strong emphasis and expired and decayed products injectable radiopharmaceuticals. In gene­ This chapter will focus on the hospital on release and recall procedures. Timing • Need for overarching audits of quality ral, radiopharmaceuticals are prepared environment, where the associated risks plays a very important role in the use of management systems for immediate use, i.e. within 24 h of are lower in comparison with industrially radiopharmaceuticals and hence there preparation. manufactured pharmaceuticals. The in- is strong need to have such procedures The commonly used radiopharmaceuti- dustrial production of radiopharmaceuti- in place. The release procedure includes CONTROL OF PREPARATION cals (technetium-99m products) and gen- cals is required to follow volume 4 of the objective assessment of the prepared PROCESSES erators (technetium/molybdenum) in hos- European EudraLex GMP guidelines [2] product. There is strong emphasis on Production operations must follow clearly pitals should have European or national and related national regulations; EudraLex ensuring that the radiopharmaceutical defined and documented procedures marketing authorisation and be prepared Annex 3 is specific to radiopharmaceuti- has been accurately prepared and to minimise the chance of errors. These in accordance with the stated product cals [3]. on appropriate compliance with procedures should ensure that the specifications. Technetium-99m prod- For nuclear medicine there are three specifications. A recall procedure must work area is clear and uncluttered. Work ucts start as sterile non-radioactive kits to EANM-associated guidelines: be documented and reviewed at least should be performed with only one which technetium-99m from the genera- • Guidance on current good radio- once a year as an insurance policy in radiopharmaceutical agent at a time and tor is added to prepare the final product. pharmacy practice for the small-scale case the product is found not to meet once the radiopharmaceutical has been The marketing authorisation determines preparation of radiopharmaceuticals specifications once all QC has been prepared there must be appropriate ‘line the radioactivity per radiopharmaceutical using automated modules: a Europe- completed. The above GMP guidelines clearance’ from the direct preparation area, kit; therefore this amount should not be an perspective (2014) [4]

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PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE sometimes called the ‘critical zone’. This micro-organisms which cause infection. patient’s dose. Dose calibrators should be marked and stored separately in restricted PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE ‘critical zone’ is the work area behind the Vials should always be wiped with a fresh cross-checked using a standard calibration areas until they have decayed before lead glass shield of the laminar airflow alcohol swab immediately before use. source at least once a day. Results must disposal. cabinet or the central area inside an The needle tip must not be allowed to be within an acceptance limit of 5%. The Therefore, the basic requirements of enclosed dispensing isolator. Long forceps touch any other surface. values from the dose calibration checks radiopharmaceutical GMP are that: or tongs should be used when lifting vials Radioactive, microbial and particulate should be plotted on a graph (i.e. trended) • All manufacturing processes, and all containing radioactive material. This will cross-contamination should be to ensure stability of the equipment. critical steps within those processes, help reduce the exposure dose or the avoided by appropriate technical or Prepared products should be held ‘in are clearly defined and documented, chance of contamination to the hands. organisational measures. These measures bond’ until all evaluation of finished and all significant changes to the Staff working in radiopharmacies should should be detailed in documented radiopharmaceutical products has been processes are validated. wear personal monitoring devices at all work instructions and all staff should be completed and documented, this being • All necessary radiopharmacy facilities times in a radiation area. When these are trained in them. Each product should a necessary step before release of the for GMP should be provided with: not being worn to monitor occupational be prepared following line clearance product for patient administration. A clear »» Appropriately qualified and exposure, they should be stored in a low- and in an orderly fashion to permit set of standards and conditions must be trained personnel radiation background area. batch segregation and stock rotation. established for this ‘final release’. »» Adequate premises and

At every stage of processing, products Prevention of product crossover and The final product should be stored space and materials should be protected from misadministration is a key challenge in appropriately, in accordance with the »» Suitable equipment (e.g. microbial and particulate contamination. most radiopharmacies across the world. instructions set out by the manufacturer L-lead screen, syringe shields, Sanitisation of all items should be In this context, appropriate labelling of the radiopharmaceutical kit. In general, shielded waste bin, long for- undertaken in at least two stages plays an important role. Labels applied radiopharmaceuticals should be kept ceps/tongs, stainless steel (with a sporicide and 70% alcohol) to containers, equipment or premises below 25oC and some should be stored in work trays, contamination prior to their use in a pharmaceutical should be clear, unambiguous and in the the refrigerator as this helps to maintain monitor, dose calibrator) and laminar air flow cabinet or isolator. The previously agreed format. In addition to high radiochemical purity. The latter is environmental services sanitisation involves a spraying and the wording on the labels, it is helpful important as radiopharmaceuticals are »» Correct materials (sealed cali- wiping technique and each operation to use colours to indicate status (e.g. mainly dispensed from multidose vials brator reference sources) should be validated for these cleanroom bone scan). Checks on the radioactivity and are used on a number of patients: »» Containers and labels practices. Care is required when using and product yields, and reconciliation it is important that the last patient also »» Approved procedures and in- sporicides as they affect radiochemical of quantities, should be carried out and receives a high-quality product. structions purity. Aseptic, microbial-free conditions documented as necessary to ensure Deviations from instructions or pro­ »» Suitable storage and trans- and techniques must be ensured when that there are no discrepancies outside cedure guidelines should be avoided port radiopharmaceuticals are reconstituted acceptable limits. as far as possible. Any deviation should or drawn up for patient administration In addition, the dose calibrator setting be approved in writing by a competent • In the light of local experience in order to prevent the introduction of should be checked when assaying the person, with the involvement of the there should be systematic review, Quality Control Department. Rejected and it should be demonstrated materials and products should be clearly that radiopharmaceutical manu-

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PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE facturing processes are capable be recorded specifically if the material is important to have completed documents undertake ‘end of broth’ testing as many PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE of consistently yielding products radioactive. before the prepared product is released for radioactive samples cannot be sent to that are of the required quality and Risk assessment and validation studies patient administration. a microbiological testing laboratory for compliant with the specifications. should be undertaken before starting to The finished products should contain normal sterility testing. use any new product in order to reinforce active ingredients that are compliant Monitoring of radiation contamination Starting materials should be purchased radiation safety and GMP. The defined with the qualitative and quantitative on surfaces in the radiopharmacy should only from approved suppliers or procedures should be recorded together composition stipulated by the marketing be done using suitable radiation monitors licensed pharmaceutical wholesalers with the results and conclusions. authorisation, are of the purity required to prevent cross-contamination of other or, where possible, directly from the and are enclosed within their proper radiopharmaceutical products and spread licensed manufacturer/producer. All containers and correctly labelled. of radioactivity to clinical areas. radiopharmaceuticals and generators QUALITY ASSURANCE AND The patient must receive the correct No batch of product is released or should have marketing authorisation and QUALITY CONTROL radiopharmaceutical at the correct dose supplied prior to certification by an the purchasing team should have clear Quality assurance and quality control (QA with a high radiochemical purity. authorised person that it is in accordance instructions and appropriate training. and QC) are that part of GMP which is The majority of radiopharmaceuticals with the requirements of the relevant For each delivery, the containers should concerned with sampling, specifications are administered by injections and authorisations.

be checked for integrity of the packaging and testing. therefore appropriate monitoring of In order to cover all contingencies, and seal and for correspondence between Radiopharmacies should have environmental conditions is important for a system should be designed to recall the delivery note and the supplier’s labels. approved standards for inspection and GMP purposes. This requires that accurate products, especially as radiopharmaceuti- QC tests should be undertaken with each receipt of all radiopharmaceutical starting and sterile doses are prepared for patient cal QC tests may require additional time. new delivery of radiopharmaceutical materials and finished products. The administration. Aseptic techniques and It is necessary to take action promptly generator and radiopharmaceutical kits. radiochemical purity testing methods, sterile and pyrogen-free ingredients are if any QC parameters are unsatisfactory Each delivery or batch of material should i.e. TLC and HPLC methods and sterility used at all times to minimise bacterial and (out-of-specification) and if products are be attributed a specific reference number testing of radiopharmaceuticals, are set pyrogen contamination. Each operator known or suspected to be defective. All in- or date, or given an identification mark out by pharmacopoeias or professional should receive training in the aseptic stances of out-of-specification results and such that it can be tracked from start to guidelines. technique, with validation using agar complaints relating to potentially defec- finish. This is important with regard to The dose calibrator and other radiation transfer plates or broth tubes. tive products must be carefully reviewed product liability, in the event that a patient monitoring devices should be cross- Regular monitoring of the environment according to written procedures. It is im- reacts to the radiopharmaceutical. calibrated with radioisotopes in use. The is essential. Agar plates exposed during portant to undertake root cause analysis. All materials and products should be dose calibrator should be checked daily preparation and found to contain Audits and self-inspections should stored under the appropriate conditions. using calibrated reference sources, e.g. pathogen species, especially Gram- be conducted in order to monitor the Refrigerated items must be maintained at -137, and trended. negative bacteria and fungal spores, will implementation of and compliance with 2o–8oC and checked and controlled 24/7. All records should be made in real time; require additional cleaning to ensure GMP principles and to identify necessary Outdated or obsolete material should the recording can be done manually appropriate sanitary conditions for corrective measures. Many countries be destroyed, and this disposal should and/or using recording instruments. It is dispensing of radiopharmaceuticals. For have adopted the International Atomic radiopharmaceuticals, it is important to Energy Agency (IAEA) guidance on quality

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CONTROL AND ONGOING PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE management audits in nuclear medicine peutic application essential. In addition, for radioprotection VALIDATION OF PREMISES AND PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE practices [8]. The radiopharmacy checklist • Operation level 3c – Synthesis of there should be rotation of staff to share EQUIPMENT is based on the IAEA operational guidance positron emission tomography radio- the radiation dose. Premises should be designed and on hospital radiopharmacy [9]; this pharmaceuticals The head of production and the head equipped so as to afford maximum protec- guidance is risk based and categorises • Staff training requirements in respect of QC are key personnel, and each must tion against the entry of unauthorised per- procedures in the field of hospital of each of these operational levels, be independent from the other. In small sons, insects or other animals. Steps should radiopharmacy according to three including with regard to QC, are doc- departments the person involved with be taken in order to prevent the entry of operational levels: umented in [10]. preparation should not be responsible for unauthorised people. Security of radioac- • Operation level 1a – Dispensing of the release of products. tivity, sealed sources and radiopharmaceu- radiopharmaceuticals purchased or The head of production and the head ticals is of paramount importance. Produc- supplied in their final form from rec- KEY PERSONNEL of QC have some shared responsibilities tion, storage and QC areas should not be ognised and/or authorised manufac- relating to GMP and quality. These may used as a right of way by personnel who turers or centralised radiopharmacies There must be sufficient qualified and include, subject to any national regulations: do not work in them. trained personnel to carry out all the • Monitoring of compliance with the Lighting, temperature, humidity and • Operation level 1b – Dispensing of ra- tasks which are required during the requirements of GMP ventilation should be appropriate and dioiodine and other ready-to-use ra- production of radiopharmaceuticals. • Approval of written procedures and such that they do not, directly or indirectly, diopharmaceuticals for radionuclide There must be staff responsible for the other documents, including amend- adversely affect the radiopharmaceutical therapy or palliation production of the product and other staff ments products during their manufacture and • Operation level 2a – Preparation of who are responsible for the quality of the • Monitoring and control of the manu- storage. The layout and design must aim radiopharmaceuticals from prepared radiopharmaceutical. facturing environment to minimise the risk of errors and permit and approved reagent kits, genera- Individual responsibilities should be • Ensuring cleaning of radiopharmacies effective cleaning and maintenance in tors and radionuclides clearly understood by the individuals and and general hygiene order to avoid cross-contamination and • Operation level 2b – Radiolabelling recorded. All personnel should be aware • Approval and monitoring of suppliers build-up of dust or dirt, which would of autologous blood cells, especially of the principles of GMP that are relevant of materials adversely affect the quality of products. white blood cells to them. Competency-based training in • Retention of records Premises and equipment must be locat- • Operation level 3a – Compounding radiopharmacy is essential to GMP [10,11] • Inspection, investigation and taking ed, designed, constructed, adapted and of radiopharmaceuticals from ingre- and all staff should receive initial and of samples, in order to monitor factors maintained to suit the radiopharmaceuti- dients and radionuclides for diagnos- continuing training, including with regard which may affect product quality cal operations to be carried out and pro- tic application to hygiene. Operators are trained to carry • Staff training vide optimal radiation protection. There out procedures correctly, and this training are specific European and national rules should be documented and regularly for the design of radiopharmacies and • Operation level 3b – Compounding updated. From a pharmaceutical point of there are different classes of the room and of radiopharmaceuticals from ingre- view, there should be a minimum number biosafety cabinets [discussion of this topic dients and radionuclides for thera- of trained staff – capacity planning is is beyond the scope of this chapter; how-

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PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE ever, for sterile preparation of radiophar- of the system of documentation utilised generator and radiopharmaceutical and recommendations. Records of any PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE maceuticals an EU Grade A environment must be to establish, control, monitor and must conform and thereby serve as a significant deviations should be retained (bacteria and particle free) is required]. record all activities which directly or indi- basis for quality evaluation. and they should provide evidence of the These specifications are in place to ensure rectly impact on all aspects of the quality • Records that provide evidence of investigation undertaken and the reasons sterile preparation of radiopharmaceu- of radiopharmaceuticals. various actions taken to demonstrate for GMP non-compliance. ticals; in addition, they should prevent The instructions and procedures compliance with instructions, e.g. A complete history of a generator cross-contamination of radiopharmaceu- [standard operating procedures (SOP)] activities, events, investigations and, and radiopharmaceutical batch to be ticals. should be written in an instructional in the case of manufactured batches, traced to patients is to be retained in a Premises should be carefully main- form in clear, stepwise and unambiguous a history of each radiopharmaceutical comprehensible and accessible form. tained, ensuring that repair and main- national language, specifically applicable batch of product, including its use in tenance operations do not present any to the facilities provided. There should patients. hazard to the quality of products. They be detailed written procedures for • Records that include all data on which SAFE AND SECURE STORAGE should be cleaned and, where applicable, cleaning, sanitisation and disinfection SOP quality management decisions are AND DISTRIBUTION OF disinfected according to detailed written according to local practice. based. RADIOPHARMACEUTICALS procedures. The radiopharmacy cleaning The storage and distribution of all • Documentation and release staff should also be trained and should The documentation types required in radioactive products should be controlled procedures which ensure that the use dedicated cleaning mops etc. that are typical radiopharmacies are: to minimise any risks with respect to necessary and relevant tests are specific to radiopharmacy and not used their quality. It is important to meet legal • Quality manual actually carried out and that their elsewhere (mainly to prevent spread of requirements. • Site plan together with organisational quality has been judged to be radioactive, microbial and particulate con- charts describing key positions and satisfactory. tamination). Cleaning materials should be operational links kept under control at all times. Any chang- • Certificates of analysis that provide GOOD PRACTICES IN RELATION es should be documented and systemati- • Work instructions, with SOP, a summary of the generator and TO WASTE AND EXPIRED AND cally followed up. covering: manufacturing formulae, kit testing results on samples of DECAYED PRODUCTS sanitisation, processing, labelling products together with evaluation of Radioactive waste should be fully and dose calibrator checking, testing compliance with stated specifications. documented and controlled at each ESSENTIAL DOCUMENTATION of radiochemical purity and final stage. This should be done in real time. Good documentation constitutes an es- release. In addition, records and reports of The level of radioactive waste is generally sential part of the QA system and is key • Protocols and associated forms that any risk assessment, environmental authorised in the site license, which covers to operating in compliance with GMP provide instructions for performing microbiology, validation, exercises, projects both intake and disposal of solid and liquid requirements. The various types of doc- and recording certain critical and or investigations should be retained. Each waste. The radiopharmacy staff have an ument and media used should be fully discrete operations. of these reports should be structured important role and they should be trained controlled and defined in the Quality • Specifications that describe in detail and should contain the following details: to ensure regulatory compliance. Management System. The main objective the requirements with which the objective, results, discussion, conclusions Only designated, labelled and properly

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REFERENCES PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE shielded containers should be used for The quality risk management system 1. Overview of EU radiation protection legislation: EJNMMI_Guidance_cGRPPfulltext_05_2010.pdf disposal of radioactive waste. All used sy- should ensure that: https://ec.europa.eu/energy/en/over 6. Guidelines on current good radiopharmacy ringe needles should be disposed of in a • Evaluation of the risk to quality is view-eu-radiation-protection-legislation. Key ref- practice (cGRPP) in the preparation of radio- separate container made of a strong ma- based on scientific knowledge and erence: Basic safety standards, 2013/59/EURATOM pharmaceuticals. EANM Radiopharmacy Com- terial to reduce the chance of injury from a experience with the process and is Council Directive of 5 December 2013 laying mittee. 2007. https://eanm.org/publications/ radioactive or contaminated needle. ultimately linked to protection of the down basic safety standards for protection guidelines/gl_radioph_cgrpp.pdf patient. against the dangers arising from exposure to 7. Pharmaceutical Inspection Convention/Phar- • The level of effort and the documen- ionising radiation, and repealing Directives maceutical Inspection Co-operation Scheme. NEED FOR OVERARCHING tation of the quality risk management 89/618/Euratom, 90/641/Euratom, 96/29/Eur- Guide to good manufacturing practice for me- AUDITS OF QUALITY process are commensurate with the atom, 97/43/Euratom and 2003/122/Euratom. dicinal products. Annex 3. Manufacture of ra- MANAGEMENT SYSTEMS level of risk. (OJ L-13 of 17/01/2014 page 1). diopharmaceuticals. https://picscheme.org/en/ Any significant deviations from instructions 2. EudraLex - Volume 4 - Good Manufacturing publications?tri=gmp and guidelines must be fully recorded and Practice (GMP) guidelines. https://ec.europa.eu/ 8. IAEA. Quality management audits in nucle- investigated. In addition, any complaints SUMMARY health/documents/eudralex/vol-4_en ar medicine practices. IAEA Human Health about radiopharmaceuticals should be This chapter has described essential GMP 3. EudraLex. The Rules Governing Medicinal Prod- Series No. 33. Vienna: IAEA; 2015. https://

properly examined, the causes of quality rules and practices for radiopharmaceuti- ucts in the European Union Volume 4. EU Guide- www-pub.iaea.org/books/iaeabooks/10714/ defects investigated and appropriate cals prepared in hospitals for use in nuclear lines to Good Manufacturing Practice Medicinal Quality-Management-Audits-in-Nuclear-Med- measures taken in respect of the defective medicine procedures and has outlined the Products for Human and Veterinary Use. Annex icine-Practices. Follow the following weblink products to prevent recurrence. necessary QC of radionuclide generators 3. Manufacture of Radiopharmaceuticals. 2008. and then click on the Excel file link: https://www. A programme of self-inspections and radiopharmaceuticals. There is a need https://ec.europa.eu/health/sites/health/files/ iaea.org/publications/10714/quality-manage- should be conducted in order to monitor for well-managed and well-controlled files/eudralex/vol-4/2008_09_annex3_en.pdf ment-audits-in-nuclear-medicine-practices?- compliance with GMP principles and documentation systems that ensure ap- 4. Aerts J, Ballinger JR, Behe M, Decristoforo C, El- supplementary=39799 to serve as the basis for proposal of propriate control of processes, premises singa PH, Faivre-Chauvet A, et al. Guidance on 9. IAEA. Operational guidance on hospital radio- corrective measures. The International and equipment at all times. Quality man- current good radiopharmacy practice for the pharmacy. A safe and effective approach. Vienna: Atomic Energy Agency (IAEA) guidance agement systems, risk assessment, self-in- small-scale preparation of radiopharmaceuticals IAEA; 2008. https://www-pub.iaea.org/MTCD/ on quality management audits in nuclear spection and external audits are an inte- using automated modules: a European perspec- Publications/PDF/Pub1342/Pub1342_web.pdf medicine practices [8], already discussed gral part of radiopharmacy practices. High tive. J Label Compd Radiopharm 2014;57:615– 10. IAEA. Competency Based Hospital Radiophar- above, is hospital specific and can be standards of practice are important for all 620. https://www.eanm.org/content-eanm/ macy Training. Training Course Series No. 39. used for self-assessment and external radiopharmaceuticals prepared for use in uploads/2016/11/JLCR_Automated_module_ Vienna: IAEA; 2010. http://www-pub.iaea. peer-reviewed audits. Reports should patients. guideline_2014.pdf org/MTCD/publications/PubDetails.asp?pu- contain all the observations made during 5. Elsinga P, Todde S, Penuelas I, Meyer G, Farstad bId=8227 the inspections and, where applicable, B, Faivre-Chauvet A, et al.; The Radiopharmacy 11. IAEA. Strategies for clinical implementation and proposals for corrective measures. Committee of the EANM. Guidance on current quality management of PET tracers. Vienna: Statements on the actions subsequently good radiopharmacy practice (cGRPP) for the IAEA; 2009. http://www-pub.iaea.org/MTCD/ taken should also be recorded. small-scale preparation of radiopharmaceuticals. publications/PubDetails.asp?pubId=7983 Eur J Nucl Med Mol Imaging 2010;37:1049–1062. https://eanm.org/publications/guidelines/5_

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TRANSLATIONAL APPROACH TO RADIO- PHARMACEUTICAL DEVELOPMENT

by Latifa Rbah-Vidal, Pedro Fragoso Costa

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INTRODUCTION RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO The translational process for radiopharmaceuticals (RPs), like that for by cell uptake studies, performed by ic the complexity of a whole organism, RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO conventional drugs, is a long and strenuous process. It starts with several incubating the radiolabelled agent (e.g. their simplicity allows procurement of ini- steps of in vitro and in vivo preclinical testing research, which must be antibody) with the cell expressing target tial information regarding the metabolism completed before clinical research can begin on an RP candidate. These (e.g. antigen). of the compound. evaluation and control steps aim to provide the necessary information for distribution and safety assessment permitting characterisation of potential Plasma protein binding In vivo evaluation adverse effects in humans. Like conventional drugs, RPs bind to Biodistribution studies plasma proteins to variable degrees. The Although in vitro and cell uptake studies Such preclinical experiments aim to receptors), the in vitro binding assay estimation of plasma protein binding is one are extremely useful, in vivo animal studies demonstrate that the radiotracer: can be performed by incubating a fixed major determinant of the RP distribution are still required before RP candidates can

• marks the targets and/or the mech- target concentration with increasing in the body. This can be assessed by progress from the stage of in vitro testing anisms which it is designed to mea- concentrations of the radiolabelled incubating the RP with fresh human to the stage of toxicity assessment and, sure (specificity) compounds. Bound radiolabelled tracer plasma and performing measurements finally, first-in-human (FIH) studies. • shows a cell-killing effect in the and free tracer are then separated by using several techniques such as dialysis, In tissue biodistribution studies, the RP case of a therapeutic RP filtration and counted for radioactivity. ultrafiltration and trichloroacetic acid is injected into disease-bearing animals • shows suitable kinetics and meta- Binding data can be analysed with curve- (TCA) precipitation. such as mice, rats or rabbits. All animal

bolic stability fitting software to calculate Kd (the ligand experiments have to be conducted in • does not display toxicity in healthy concentration that binds to half the Metabolic stability accordance with the European guidelines

tissues and organs receptor sites at equilibrium) and Bmax (the Another aspect to be considered in the (2010/63/UE) [2] and have to be approved • uptake is modulated by changes of maximum number of binding sites) to preclinical development of an RP candidate by the national or local animal use ethics target expression (sensitivity) determine affinity. is the metabolism. Metabolic stability can committee. Binding potential (BP) is the ratio of be assessed in vitro using human liver This preclinical evaluation process

Bmax (receptor density) to KD (radioligand microsomes containing cytochrome P450 often starts with imaging studies (PET or EVALUATION STEPS NEEDED equilibrium dissociation constant), as (CYP, a dominant group of metabolising SPECT imaging) which can be coupled FOR CLINICAL TRANSLATION defined by Mintun et al. [1]: enzymes) or other subcellular hepatic with autoradiography on tissue sections fractions which contain non-CYP enzymes or ex vivo biodistribution studies, in In vitro evaluation (such as acetyl transferase or glucuronyl which organs are harvested, weighed Molecular targeting transferase) involved in drug metabolism. and counted for radioactivity following One of the first aspects to take into Hepatocytes and liver slices can also the injection of a radiotracer. All these

account when developing a new imaging where Bmax is the total density be used and are physiologically more methods are aimed at confirming that or therapeutic RP is the high uptake or (concentration) of receptors in a sample relevant for measurement of the hepatic the RP interacts (in vivo or ex vivo) with

tropism for the potential target site, and of tissue, KD is the (radioligand) equilibrium metabolism of RP. the intended target (affinity) and shows the need to prove that the RP specifically dissociation constant and the affinity of Although in vitro and ex vivo experi- minimal uptake in healthy tissues.

marks what it is designed to measure. ligand binding is the inverse of KD. mental models can never accurately mim- RP specificity for the target can also be For (RPs which bind to Targeting potential can also be assessed

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RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO evaluated in vivo by imaging techniques • Dynamic acquisition mode: In stability) and bioanalytical methods and • If the non-radioactive compound is RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO using animal models expressing a this acquisition mode, images are pharmacokinetic/pharmacodynamic (PK/ unknown and no preclinical toxicity modulation of target levels through acquired according to a predefined PD) modelling. data are available, then full toxicity under- or overexpression (such as tumour, temporal framing scheme (one studies have to be performed and overexpressed receptor). Note that, acquisition interval). This mode is Animal toxicity studies conducted under Good Laboratory interestingly, RP uptake can be compared used when it is necessary to follow Before an investigational RP can be Practice (GLP) regulations. with that observed in “knock-out” mice the uptake and clearance of an administered to humans as part of an FIH which do not express the target of the RP. RP over an extended period. It trial, it must undergo safety testing in non- In general, it is recommended that Imaging is usually performed in the provides more information on the clinical studies [3]. RPs are a special class toxicity tests are carried out in two static or dynamic acquisition mode: kinetics of the RP by using absolute of drugs comprising two parts, one “cold” different mammalian species (one rodent

PET quantification and modelling. or non-radioactive (e.g. antibody, peptide) and one non-rodent) and that the risk of • Static acquisition mode: This is Indeed, pharmacokinetics (PK) and one radioactive (e.g. fluorine-18, RP overdose is evaluated. This has in the the basic acquisition mode, where parameters (clearance, volume of copper-64, gallium-68, iodine-131, past been achieved by injecting an acute the radiotracer distribution is distribution, etc.) of the radiotracer -225). Thus, the toxicity of RPs may dose of RP and monitoring animals for assumed to be static throughout the can be evaluated from these be driven by the non-radioactive as well as clinical signs and changes in parameters acquisition. In this mode, a single biodistribution studies. The the radioactive component. Considering such as body weight and food intake, with image is generated representing elimination half-life can be measured the first version of the new guideline on subsequent post-mortem examination. the radiotracer distribution over the by collecting serial samples of non-clinical requirements for RPs [4], three Today, however, this approach has largely complete acquisition time. Acquired blood at different time intervals schemes are possible: been replaced by so-called extended images are then processed by after radiotracer administration • If the non-radioactive part of the RP is single-dose toxicity studies entailing dedicated software for radioactive and measuring the plasma a known compound and if preclinical assessment in only one mammalian signal quantification. Usually, a semi- radioactivity. Urinary and faecal studies are available, then there is no species – usually a rodent with evaluation quantitative analysis is performed excretion can also be determined need for additional toxicity studies at day 1 and 14 days post dose and the results are expressed in quantitatively by collecting urine if there is available information administration to assess acute and delayed terms of the standardised uptake and faeces at defined intervals after or data demonstrating that the toxicity and/or recovery. Recently, a new value (SUV), which is the ratio of RP administration and measuring radioactive atom does not change approach (summarised in Table 1) has the image-derived radioactivity radioactivity in the samples. the pharmacology of the compound. been proposed, based on the definition concentration in a region of interest • If minimal modification of the of three distinct toxicological limits [5]: to the whole body concentration of Even if PK evaluation in animals is structure of the non-radioactive toxicological limit 1 <1.5 μg, toxicological the injected radioactivity and body still mandatory in the preclinical data compound has been performed limit 2 <100 μg and toxicological limit 3 weight, or the percentage of the package, estimation of PK in humans (this is sometimes necessary for >100 μg. injected radioactivity per gram of can also benefit from in vitro studies radiochemistry), then the possible risk Therapeutic RPs are regarded in every organ or tissue (%ID/g). (e.g. regarding solubility, plasma related to that modification has to be respect in the same way as any other considered. medicinal product and therefore clinical

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RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO trials must comply with regulations proposed as a powerful complementary human body exposure is limited, so no Production RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO regarding investigational medicinal tool to the existing approaches, and is therapeutic, toxic or radiotoxic effects are In the clinic, RP synthesis requires much products (IMPs). The mutagenic and often achievable with PET agents [10, expected. higher levels of radioactive materials, carcinogenic potential of the non- 11]. The approach is known as human To sum up, taking a RP from the bed fast reaction times and reproducible re- radioactive component may be evaluated “microdosing studies” according to the to the bedside involves several steps in sults. Hence, it is mandatory to develop a and studies should be designed to assess European Medicines Agency (EMA) or as development, evaluation and control, straightforward GMP-compliant radiosyn- the radiation exposure of tissues due to “exploratory clinical trials” according to the entailing the participation of different thesis using fully automated radiosynthe- the radioactive part, in order to predict Food and Drug Administration (FDA). Both disciplines, as illustrated in Figure 1. sisers and including suitable procedures the radioactive exposure in humans and the EMA in 2004 [12] and the US FDA in for quality control. to mitigate radiation-induced toxicity. 2006 [13] recognised the concept and its

Note that the radiation is a major legitimacy with respect to the conduct of GOOD MANUFACTURING Quality control contributor to cancer induction, so such studies. It is important to note that PRACTICE (GMP) FOR RPS All quality control procedures that are dosimetric considerations can cover the microdosing clinical studies are not meant Beside their efficacy for specific indications, applied to non-radioactive drugs are carcinogenic potential of the RP. Note also to replace traditional phase 1 clinical trials. RPs intended for use in humans should be applicable to RPs. Furthermore, since most that radiation-induced clinical toxicity is The use of microdosing studies can be sterile, pyrogen-free and safe. This implies RPs are short-lived products, the methods covered by Directive 2013/59/Euratom [8]. considered in the development process that RP production should be transferred used for quality control should be fast and for RPs. In this case, very low single doses from the conventional laboratory to a GMP effective. Usually, tests must be completed Microdosing studies of the tested RP are administered to very facility with a controlled environment, before release of the drug product; The concept of microdosing assumes few human subjects (healthy volunteers where manufacturing and quality control however, some RPs with very short half- that key PK parameters of a new chemical or patients) to investigate target receptor can be undertaken in a way compliant lives may have to be released and used entity (NCE) that is developed as a drug binding or tissue distribution in a PET study with the legal framework and regulatory after assessment of batch documentation can be evaluated using very small doses and/or to obtain basic PK parameters procedures and in accordance with the even if all quality control tests have not (microdoses) of the investigational (such as volume of distribution, clearance principles of GMP for medicinal products been completed. The necessary steps in

compound. Since such low doses and t1/2) without the introduction of [15]. quality control are summarised in Table 2. are likely to be too small to have any pharmacological effects. GMP requires dedicated clean room Additionally, GMP and the Clinical pharmacodynamic effects or cause any According to the EMA, a microdose is facilities with the highest classification Trials Regulation impose the need for major after a single dose, it defined as less than 1/100th of the dose to ensure aseptic preparation of RPs. authorisation and require that a qualified should be possible to undertake such calculated to yield a pharmacological Preparation and quality control of RPs person, according to Directive 2001/83, is studies in humans without having to effect of the test substance. This should be conducted only by competent responsible for the release of RPs. perform the classical toxicology studies calculation is based on primary PD data and appropriately qualified personnel. The at therapeutically effective doses that are obtained by in vitro and in vivo studies. person responsible for preparation should Quality assurance mandated prior to regular phase 1 trials. Typically, the maximum dose must be less be clearly identified and ideally should not Furthermore, GMP implies the need for This new approach, developed than 100 μg or 30 nMol [14]. The use of be the same person as is responsible for a highly sophisticated quality manage- almost two decades ago [9], has been such a low amount of the RP means that quality control. ment framework where all the operations concerning production and manufacture

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RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO as well as quality control have to be doc- Acquisition of informed consent from • Blood/urine sampling intervals for into consideration the pharmacological RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO umented and accurately recorded. Prior the healthy volunteer or patient is also pharmacokinetic study effect of the drug, so the starting dose, to clinical trials, standard operating pro- mandatory. • Safety profile maximum dose and exposure and cedures (SOP) for the preparation, quality As RP imaging agents are usually em- maximum duration of treatment are control and quality assurance of RPs, as ployed at an extremely small mass dose FIH study design for diagnostic radio- carefully considered. Also, beside the well as specifications for starting materials, (in the nanogram to microgram range) tracers is quite straightforward compared route and frequency of administrations, should be in place. This ensures harmoni- with no pharmacological effects, a very with interventional drug FIH clinical trials, the half-time and washout time of the sation of practice, traceability and mainte- low incidence of adverse events and a where, for instance, healthy volunteers or IMP are determined, as are the sequence nance of standards. short half-life, FIH studies aim to provide patients receive a single dose of the inves- and interval between dosing of subjects information on feasibility, target specifici- tigational drug or a placebo, starting with within the same cohort. In the case of

ty, stability, safety biodistribution, pharma- a very low dose for the first cohort. There- dose escalation increments, decisions cokinetics and metabolism. Radiation do- after, the dose is escalated in the following on transition to the next dose increment FIRST-IN-HUMAN IMAGING simetry information regarding use of the cohorts (or stopped depending on the cohort or next study part (if the FIH study STUDIES RP in humans is also obtained to uncover and safety). Single ascending includes several parts) must take into Before its use in FIH clinical trials, the RP any side effects. dose studies are usually followed by multi- account tolerability and safety; moreover, has to be classified as an “investigational The following are key aspects in the ple ascending dose studies in a very similar stopping rules and the safety parameters medicinal product” (IMP) and several man- design of an FIH study: design, where the subjects receive multi- that require monitoring have to be clearly datory documents, including an Investiga- • Study population: healthy volunteers ple doses of the drug (or placebo). established. Note that even if FIH clinical tor’s Brochure (IB) and an Investigational and/or patients can be enrolled in FIH trials should be designed in a trials are primarily designed to assess the Medicinal Product Dossier (IMPD), have to one or multiple cohorts way that permits optimal results from safety and tolerability of an interventional be prepared and submitted to the com- • Demographic information from each the study, without exposing excessive drug, the PK and, when appropriate and petent authorities and the ethics commit- subject (weight, body surface, age, numbers of subjects and while ensuring feasible, the PD are often included in order tee to obtain written approval. The IMPD gender etc.) their safety. Thus, the EMA advises that to facilitate the link with the non-clinical should include all the useful information • Test RP and reference radiotracers it is usually appropriate to design the data and support dose escalation decisions. relating to the chemical and the RP quality (e.g. test compared with 18F-FDG), or administration of the first dose so that For both radiotracers and interventional of the compound, as well as non-clinical a standard of reference (histology or a single subject receives a single dose of drugs, the study design should take into data relating to pharmacology, pharma- radiological imaging) the active IMP, with justification of the consideration all the acquired preclinical cokinetics, toxicology and dosimetry [16]. • Administered dose: usually, a period of observation before the next knowledge, incorporating all available Guidance on the preparation of single dose is administered via the subject receives a dose. This is in order toxicology and pharmacology information IMPDs for RPs was published by the intravenous route to mitigate the risks associated with on the compound candidate to ensure the Radiopharmacy Committee of the EANM • Choice of imaging parameters exposing all subjects in the same cohort safety of the subjects. in 2014 [17]. Furthermore, a detailed study (scan duration, acquisition mode, simultaneously [18]. protocol has to be prepared in which number of scans per subject) for In contrast to imaging studies, the FIH every step of the protocol is documented. biodistribution and dosimetry design of interventional drug studies takes

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Compounds under Compounds above Parameter Evaluation methods/ objectives Compounds under <100 µg <1.5 µg 100 µg

RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO Evaluated by visual inspection: the solution must be clear and free from visible RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO Appearance One can consider that Potential chemical toxicity particles. there is no risk The microdosing approach can be considered [7]. In studies have to be per- pH is verified using paper strips. Initially, the pH paper should be validated against standard buffers and should be in the physiologically acceptable range (5.5–8). this case, two different approaches are possible: formed, including extend- pH (no genotoxic impurity ed single dose toxicity related risk if <2 mg Approach 1: Approach 2: studies [18] in rodent and The purity of the precursor is determined by proton NMR and elemental analysis. [5, 6]). This test is done once per batch of precursor. non-rodent species in Chemical purity Would involve not more Consists in a maximum addition to genotoxicity than a total dose of 100 of 5 administrations with assessment (Ames). Radiochemical purity is assessed by HPLC and radio-TLC. µg, more than 1/100th of washout periods (>6 Radiochemical purity/ yield the non-observed ad- half-lives), with a total verse effect level (NOAEL) cumulative dose of <500 Radiochemical stability is often tested in serum and saline using HPLC with a Given that RPs are not radioactivity detector or TLC and a radioactivity scanner (radio-TLC). or more than 1/100th of µg and with each admin- Radiochemical stability usually administered to the pharmacologically istration <1/100th of the pregnant women, there is active dose. NOAEL and <1/100th of Radionuclide purity can be determined by gamma spectrometry or by determi- no need for teratogenicity nation of the half-life. the pharmacologically Radionuclide purity studies. As RPs are given active dose. as low doses (exposure is Toxicology studies limited to a single dose or Residual solvents (e.g. Presence of residual solvents is evaluated by gas chromatography. acetonitrile and dehy- consist in extended a few doses), there is no drated alcohol) single-dose toxicity Toxicology studies con- need for either genotoxicity Bacterial endotoxins: the limulus amoebocyte lysate test is the most popular. studies in one species, sist in a 7-day repeated or carcinogenicity studies. Microbiology usually a rodent, with dose toxicity study in one Chronic toxicity studies are evaluation 14 days post species, usually a rodent, also usually not necessary. dose to assess delayed and genotoxicity studies Sterility testing must be initiated after several hours of preparation. To assure ste- rility, each batch of product has to be tested using culture vials with aerobic and toxicity and/or recovery. are not recommended. Sterility anaerobic materials and incubated with culture vials for at least 4 days at 37°C. Genotoxicity studies For highly radioactive Sterility is assayed by visualising the cloudiness of the solution. are not recommended. compounds such as PET For highly radioactive probes, appropriate PK Table 2: The necessary steps in quality control for PRs used in the clinic compounds such as PET and dosimetry should be probes, appropriate PK performed. and dosimetry should be performed.

Table 1: Possible approaches for toxicity evaluation depending on the mass of the compound

146 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 147 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 11 CHAPTER 11

REFERENCES

1. Mintun MA, Raichle ME, Kilbourn MR, Wooten 11. Wagner CC, Langer O. Approaches using mo- lecular imaging technology – use of PET in

RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO GF, Welch MJ. A quantitative model for the in RADIOPHARMACEUTICAL DEVELOPMENT TRANSLATIONALAPPROACH TO vivo assessment of drug binding sites with clinical microdose studies. Adv Drug Deliv Rev positron emission tomography. Ann Neurol 2011;63:539–546. 1984;15:217–227. 12. CPMP/SWP/2599/02/Rev1. Position Paper on 2. Implementation, interpretation and terminol- nonclinical safety studies to support clinical ogy of Directive 2010/63/EU. http://ec.europa. trials with a single microdose. European Med- eu/environment/chemicals/lab_animals/inter- icines Agency (EMEA), Committee for Medic- pretation_en.htm. inal Products for Human Use (CHMP) 2004. 3. International Conference on Harmonisation http://www.emea.europa.eu/pdfs/human/ 2009. Guidance on nonclinical safety studies for swp/259902 en.pdf. the conduct of human clinical trials and market- 13. Center for Drug Evaluation and Research. Guid- ing authorisation for pharmaceuticals M3(R2). ance for industry, investigators, and review- Step 4 Geneva: ICH. ers – exploratory IND studies. Center for Drug Evaluation and Research (CDER), Food and Drug

4. Guideline on the non-clinical requirements for radiopharmaceuticals. EMA/CHMP/SWP/ Administration, US Department of Health and 686140/2018EMA/CHMP-SWP/686140/2018. Human Services. 2006. http://www.fda.gov/ 5. Koziorowski J, Behe M, Decristoforo C, Ballinger cder/guidance/7086fnl.htm. J, Elsinga P, Ferrari V, et al. Position paper on 14. Guidance for industry, investigators and review- requirements for toxicological studies in the ers: exploratory IND studies. Jan 2006. http:// specific case of radiopharmaceuticals. EJNMMI www.fda.gov/downloads/drugs/guidance- Radiopharm Chem 2017;1:1. complianceregulatoryinformation/guidances/ 6. ICH Q3B (R2). Note for guidance in new drug ucm078933.pdf products (CPMP/ICH 2738/99). https://www. 15. EMEA/CHMP/QWP/306970/2007: Guideline on ema.europa.eu/en/ich-q3b-r2-impurities-new- radiopharmaceuticals. 16. European Medicines Agency Committee for Figure 1: Schematic of the RP evaluation steps needed for clinical translation drug-products 7. ICH-M3 (R2) Nonclinical Safety Studies for the Medicinal Products for Human Use. Guideline Conduct of Human Clinical Trials and Marketing on the requirements for quality documen- Authorization for Pharmaceuticals. EMA/CPMP/ tation concerning investigational medicinal ICH/286/1995. products in clinical trials (2012). EMA/CHMP/ 8. Directives of the European Atomic Energy BWP/534898/2008. http://www.ema.europa. Community (EURATOM) (Directive 2013/59/ eu/docs/en_GB/document_library/Scientific_ Euratom). guideline/2012/05/WC500127370.pdf 9. Lesko LJ, Rowland M, Peck CC, Blaschke TF, Bre- 17. Todde S, Windhorst AD, Behe M, Bormans G, imer D, de Jong HJ, et al. Optimizing the science Decristoforo C, Faivre-Chauvet A et al. EANM of drug development: opportunities for better guideline for the preparation of an Investiga- candidate selection and accelerated evaluation tional Medicinal Product Dossier (IMPD). Eur J in humans. Eur J Pharm Sci 2000;10:iv–xiv. Nucl Med Mol Imaging 2014;41:2175–2185. 10. European Medicines Agency. ICH guideline 18. Guideline on strategies to identify and mitigate M3(R2) on non-clinical safety studies for the risks for first-in-human and early clinical trials conduct of human clinical trials and marketing with investigational medicinal products EMEA/ authorisation for pharmaceuticals. EMA/CPMP/ CHMP/SWP/28367/07 Rev.1. ICH/286/1995. Dec 2009. http://www.ema.eu- ropa.eu/docs/en_GB/document_library/Scien- tific-guideline/2009/09/WC500002720.pdf.

148 EANM TECHNOLGIST’S GUIDE EANM TECHNOLGIST’S GUIDE 149 RADIOPHARMACY: AN UPDATE RADIOPHARMACY: AN UPDATE CHAPTER 10 IMPRINT PHARMACEUTICALS WITHIN THE HOSPITAL ENVIRONMENT GOOD MANUFACTURING FOR RADIO- PRACTICE Publisher: European Association of Nuclear Medicine Schmalzhofgasse 26, 1060 Vienna, Austria Phone: +43-1-890 27 44 | Fax: +43-1-890 44 27-9 Email: [email protected] | URL: www.eanm.org

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