NUCLEAR APPLICATIONS IN HEALTH CARE LASTING BENEFITS BY STEFFEN GROTH

uclear applications in and well established radionuclides by using health care have a time- applications in view of new instruments like rectilinear Nhonoured record of directions that are emerging. scanners or gamma cameras. being highly cost-effective in Probably the major addressing important health MEDICAL DIAGNOSIS characteristics of in vivo nuclear problems such as malnutrition, Diagnostic applications medicine procedures is that the cancer, infectious and comprise in vivo and in vitro amount of radiopharmaceutical circulatory diseases. Today methods. The in vivo needed for in vivo diagnostic they are providing lasting applications are characterized by studies is very tiny and always in benefits for patients, the administration of a the range of physiological physicians, medical researchers, radiopharmaceutical to the quantities. For instance, for a and health care practitioners patient and usually subsequent thyroid scintigraphy, the amount throughout the world. external detection with a gamma of radioactive iodine employed is Many nuclear applications camera or some other detector. over a thousand-fold less than have become so well- The in vitro applications involve the amount of iodine daily taken established and documented analysis of samples taken from up with food. It therefore has that they are preferred to other the patient, most often blood no measurable interference with methods. This is because they samples. thyroid function and no side 33 frequently provide unique In vivo Applications. In vivo effects. medical information, or are applications are a major Also, the radioactive dose among the least expensive nuclear medicine technology. received by the patient for approaches to a problem. The principal role of these scintigraphies is, in most cases, Some applications -- originally procedures is the assessment of negligible. As a rule of thumb, introduced as nuclear techniques organ function. Radionuclides it approximates the dose -- have developed into or compounds that are labelled received from one year of applications that have no with radionuclides are natural background radiation “nuclear” component as such. administered to the patients to per examination. (For example, many routine allow specific organ function to The in vivo method provides radioimmunoassays, or RIAs, be evaluated by tracing the for studying a number of have later developed into dynamic biodistribution of organs and systems. The major enzyme-linked immunoassay, or such a compound in specific fields of application are ELISA methods.) This organs. Tracing of the oncology, endocrinology, development often occurred for compound is achieved by cardiology, and nephro- reasons of high-speed external detection of the urology. The most widely automation and/or simplicity. At photon emitted from the applied instruments and in the same time, however, robustness and precision often Mr. Groth is Director of the IAEA Division of Human Health. were sacrificed. Contributors to the article were Mr. Ajit Padhy, Head of the Nuclear applications in Division’s Nuclear Medicine Section; Mr. Victor Levin, Head of the health care can be roughly Division’s Radiation Biology & Therapy Section; Mr. Venkatesh divided into diagnostic, Iyengar, Head of the Division’s Nutrition, Health, & Environmental therapeutic, and preventive Studies Section; Mr. Pedro Andreo, Head of the Dosimetry & Medical applications. This article Radiation Physics Section, and Ms. Baldip Khan and Mr. Soo Ling describes a series of successful Ch’ng, staff members of the Division. IAEA BULLETIN, 42/1/2000 blood pressure, diabetes or PET is available only in a kidney stones. limited number of developing ■Thyroid scanning is countries since the technology commonly used for the is expensive and the screening of hyperthyroidism radiopharmaceuticals difficult and searching for possible to produce. It is envisaged, malignant thyroid tumours in however, that following the patients with nodular goitre. current clinical success, the ■ Brain scanning provides technology will continue to be important information in made widely available, vivo technologies for nuclear patients with stroke, epilepsy especially in oncology, medicine diagnostics constitute and Alzheimer’s disease. neurology, and cardiology. a formidable list. (See box, pages ■ Perfusion lung scanning, The receptor ligand 38 & 39.) in combination with radiopharmaceuticals bind ■ Bone scanning is probably ventilation lung scanning, is selectively to specific cells or the technique most commonly the most efficient technique tissues. They bear the unique performed. This is a very for the study of pulmonary feature of allowing in vivo efficient approach to look at embolism. This is a dangerous identification of the presence the function of the bones: any condition originating from of specific types of tissue whose significant injury to the bone blood clots that requires early presence is suspected (such as will cause an increase in bone intensive treatment. infected tissue.) metabolism that can be Diagnostic procedures in Also being developed is a detected by the bone scan. inflammatory or infection series of new tumour seeking The method is the most diseases play an increasingly radiopharmaceuticals. By a efficient way to search for bone important role in nuclear single injection of the relevant metastases in many types of medicine. In most cases radiopharmaceutical, the entire 34 tumours. It is also used in inflammation can be diagnosed body can be scanned for the orthopaedics for the study of by clinical examination and presence of tumour cells. For fractures, osteomyelitis or joint routine laboratory analysis. Not certain kinds of tumours called replacements. infrequently, however, nuclear neuroendocrine tumours, these ■ Myocardial perfusion medicine techniques are required techniques are already scanning is another frequently to confirm and evaluate the dramatically changing the performed nuclear medicine presence, the extent, and the diagnostic approach to the technique. This test informs severity of the process. patient. about the presence of heart Emerging Directions. Nuclear In vitro Applications. These infarction. If a patient suffers techniques developed applications include: from chest pain, the test will particularly over the past ■ Radioimmunoasssay (RIA). help clarify whether it relates decade hold great potential for Immunoassays in a variety of to reduced blood flow to the future applications. These forms have gained widespread coronaries (arteries of the include an explosion in the usage in both nuclear medicine myocardium). use of positron emission and clinical pathology. Four ■ Renal scintigraphy tomography (PET) and the main attributes account for their provides a detailed description development of receptor ligand successful application in of renal function, from blood radiopharmaceuticals. diagnostic services, these being supply to urine formation and PET allows a more accurate their sensitivity, specificity, excretion. It is very useful for visualization of the organ precision, and convenience. The the study of kidney function in under study than can be first three are inherent patients suffering from elevated obtained with the usual consequences of the gamma camera. It can also fundamental properties of the Photo: Nuclear imaging provide information on interactions between antibodies techniques provide key metabolic functions that is and their ligands which form information for diagnosing a wide impossible to obtain with other the basis of immunoassay IAEA BULLETIN, 42/1/2000 range of illnesses. (Credit: IAEA) techniques. For the time being, systems. Immunoassay is an analytical technique for quantification of the biomolecule at picogram/femtogram concentration. RIA is used to detect and quantify drugs, intermediate metabolites, steroids, peptide hormones, enzymes, cancer markers, viral antigens, cellular receptors and deoxyribo nucleic acid (DNA) molecules for early clinical laboratory diagnosis of new data, and evidence-based PCR is also being used for diseases or recurrence of RIA. detecting sub-species variation previous pathologies. In ■ Molecular Biology which can be important in the monoclonal antibody work, it Techniques using Radionuclide prognosis of cervical cancer is the most sensitive and cost Methods. Over the past several and of Hepatitis B & C. effective method for screening years, the development and The efficacy of treatment can hybridoma cell line which application of molecular be effectively monitored produces the antibody. diagnostic techniques has through quantitative PCR in Currently it is one of the initiated a revolution in the hepatitis. Direct detection of preferred conventional diagnosis and monitoring of mutations responsible for drug methods used in diseases. Polymerase chain resistance in malaria and pharmaceutical work on new reaction (PCR) is one of the tuberculosis is being carried drug development. best and most commonly out using mutation specific Since it is an isotopic assay, the applied examples of clinical PCR, and PCR coupled with radioactive signal of the probe is applications of molecular what is known as Dot-Blot 35 not subjected to usual techniques in human health. hybridization, respectively. interference; for example, by The heart of the technology Diagnosis of genetic defects -- water impurity, enzyme poisons relies on the repeated for example, in thalassemia and and other unforeseen side enzymatic amplification of the muscular dystrophy, the latter reactions. The method is targeted sequence of DNA using multiplex PCR -- also is therefore regarded as the gold fragment. The final product being carried out. It has standard by the practitioner of can be visualized by ethidium enabled some countries to set the art of immunoassay. It can bromide staining after up genetic counselling be modularly automated using a electrophoretic separation by programmes. robotic sampler for large-scale means of a radioisotopically Besides PCR, other screening of treatable diseases labelled DNA probe (see photo) molecular techniques include using minimal human resources. or detected by direct sequence single strand confirmation Emerging Directions. The analysis. Phosphorus-32 and polymorphism (SSCP) and emerging trends in RIA point sulphur-35 are the commonly protein truncation tests. They to greater sophistication. used radioisotopes. are being used to further refine They include optimization of PCR has found many diagnosis in muscular monoclonal antibody applications in both basic dystrophy. PCR is being used secretion, synthetic novel research and clinical settings. to detect malignant cells in binders, novel immobilisation In the Agency’s programme, patients with leukemias that techniques, detection of new PCR technology is being used are characterized by consistent markers of neoplastic, for the diagnosis of infectious translocation break points. degenerative, metabolic and diseases such as Chagas disease, endocrinological diseases, Leishmaniosis, Hepatitis B and Photo: An autoradiography of screening technology, global Tuberculosis. Reverse Hepatitis B samples using validation and cognitive transcriptase PCR is being used phosphorus-32 and the Dot-Blot apprenticeship of clinical RIA to detect Hepatitis C virus. hybridization technique. IAEA BULLETIN, 42/1/2000 Primers that span the ■ Measurement of Stable importance. Similarly, up to breakpoint are added to a bone Isotopes. Measurement of staple 300 million adults are likely to marrow sample and subjected isotopes by nuclear and related be affected by diabetes in the to multiple cycles of PCR. techniques have gained next two decades and Even one cell in a million with widespread strategic application therefore, prevention and translocation can be detected. in a variety of health problems management of overweight EmergingTrends. In the near through analysis of trace (obesity) is of critical future, more than one hundred elements. (See box, page importance. thousand genes will be 37.)These techniques are now For women and children, characterized under the human generally considered the best deprivation of proper nutrition genome project. Bacterial, methods for measuring the has enormous consequences. protozoan, helminth, viral and uptake and bioavailability of There is clear evidence of fungal genomes have already many important vitamins and developing countries having been or will be elucidated very nutrients. higher prevalence of low birth soon. The most important Commonly used techniques weight babies compared with application of this variety of applied for these purposes developed ones. The sequences will is expected to be include neutron activation prevalence of intrauterine in diagnostics. analysis (radiochemical and growth retardation in most Other increasingly important instrumental), Inductively developing countries also is applications will be the detection Coupled Plasma Mass recognized as a public health of prognostic markers for cancer, Spectrometry, Particle-Induced problem of great concern. drug resistance indicators, X-ray Emission, dual energy X- predictive markers for malignant ray absorptiometry, Particle- MEDICAL TREATMENT and degenerative disorders, Induced Gamma-ray Emission, Therapeutic applications of models for molecular modelling Energy Dispersive X-ray nuclear and radiation for drug design, gene therapy, Fluorescence Analysis, and techniques are advancing. 36 detection of minimal residual Total Reflection X-ray Radiation does not selectively disease, molecular Fluorescence. kill cancer cells; with sufficient epidemiological information and Emerging trends. Isotopic dose it kills all dividing cells. control measures and detection techniques in many cases have Developments in imaging of new emerging diseases. just begun to be applied in using computer tomography A number of technologies developing countries. Their use (CT) scanning and magnetic are most likely be used in the carries the potential of resonance imaging (MRI) have above applications. They are: benefiting millions through improved the definition of the quantitative, multiplex and in improved nutrition and margins of cancers. This, in situ PCR; multiplex DNA nutrition monitoring turn, has stimulated efforts to sequencing and diagnostics by techniques. They can also develop therapy planning hybridization with enriched serve to yield specific systems and equipment capable stable isotope labels using indicators of broader social and of treating the tumour to mass spectrometry; peptide economic advances. Important higher doses without increasing nucleic acids probes that areas for strategic monitoring the dose to healthy provide faster results than include health care for the surrounding organs. traditional DNA probes; elderly, and for young children The most common techniques DNA bio-chip technology and women. involve delivery of radiation where distinct probes can be Health care for the elderly from a distance -- called linked to an inert support and will be a growing concern, teletherapy -- and inserting hybridized with the test DNA since by 2025 there will be 1.2 radioactive sources into cavities from clinical samples; billion elderly people in the adjacent to tumours or even phosphor-imagers that detect world (60% of them in invasively directly into tumours beta and gamma radiation developing countries). Hence -- called brachytherapy. Other more rapidly; protein preventive measures through applications involve open truncation tests; and nutritional and other health radioactive sources for radiation IAEA BULLETIN, 42/1/2000 functional genomics. monitoring will gain therapy of cancer, and some STRATEGIC HEALTH APPLICATIONS OF STABLE ISOTOPES

■ Targeting Malnutrition: Nearly 200 million children (over 150 million in Asia and about 27 million in Africa) under 5 years of age are affected. Assessment of vitamin A is an important requirement in this context. About 90% of the body’s vitamin A is stored in the liver, and direct measurement of liver vitamin A would require invasive procedures (for example, biopsy of the liver). The IAEA has been developing far less invasive isotopic tracer techniques for measuring whole body vitamin A under conditions of supplementation (Ghana, Peru), food fortification becoming effective tools to assess obesity. There are no (Peru, Israel) and dietary improvement (China, alternatives to the isotopic methods for measuring Thailand, Philippines and India) for addressing energy expenditure under everyday living conditions. 2 18 problems of vitamin A nutrition in children and The doubly labelled water method ( H2 O) is the only pregnant or lactating women. Similarly, assessment technique that can accurately determine the energy of iron absorption from diets to evaluate its needs of people in their own environments and is one bioavailability is an important nutritional of the most reliable methods for determining food measurement. Stable isotopes provide the only energy intake. This method is gaining wider direct way for measuring iron uptake and acceptance since it is inexpensive, accurate, and can bioavailability and are regarded as a kind of “gold be applied under field conditions. standard” for iron studies in humans. Isotopic ■ Helicobacter pylori (Hp): Young children in methods are very useful for measuring absorption of developing countries suffer from high prevalence of zinc from foods, and measurement of breast milk this infection that makes them susceptible to diarrhoeal 37 intake by infants. diseases. According to 1993 statistics, persistent ■ Osteoporosis: This disorder affects elderly people diarrhoea accounted for over 60% of infant diarrhoeal (particularly post-menopausal women). The IAEA deaths in Brazil, 47% in India, 36% in Senegal, and has helped several developing countries in applying 26% in Bangladesh. Stable isotope techniques have dual energy X-ray absorptiometry (DEXA) for bone been recognized as the best and most cost effective density measurements for investigating how bone modes of diagnosis of Hp through a simple breath test mineral density varies with age, sex, ethnicity and using carbon-13 enriched substrates and measurement geographical origin of subjects. of labelled carbon dioxide. ■ Obesity: This is linked to cardiovascular diseases, hypertension, and maturity on-set diabetes mellitus, Photo: Health practitioners in many countries are among many others; stable isotope-based techniques are being trained to use isotope techniques effectively. thyroid diseases. (See table, reaching deeper-seated tumours function. Early cancers of the page 40.) with improved accuracy. larynx are treated with ■ Teletherapy. Teletherapy has Earlier treatment equipment radiotherapy to preserve the evolved from treatment using X- was highly effective for smaller voice, and early breast cancer is ray tubes, to treatment involving superficial tumours; it was so treated by removal of the lump cobalt machines, where radiation effective that skin tumours and radiation rather than was derived from radioactive treated by radiotherapy or mastectomy. cobalt sources (gamma rays), and surgery are expected to be As imaging and treatment then back to using X-rays that cured and only melanomas of improved, this trend towards now are produced by linear the skin are included in cancer minimal surgery augmented by accelerators. These machines registers. Increased emphasis is radiotherapy has increased for produce more penetrating and being placed on cosmetic deeper tumours. Sites ranging very sharp beam edges capable of results and retention of from the prostate to the head IAEA BULLETIN, 42/1/2000 NUCLEAR APPLICATIONS IN HEALTH CARE ■ Static Gamma Camera Imaging emitting isotope with a tracer that is selective for Principle: Gamma camera converts photons a specific biochemical pathway, it is possible to emitted from a radiopharmaceutical administered estimate absolute rates of biological processes, to a patient, presenting an image of the element’s such as rates of glucose utilization, protein distribution. Application: Static and dynamic synthesis, oxygen consumption, and blood flow. imaging of organ functions. Comparative Comparative Advantage: PET is unique in its Advantage: High-quality images. ability to create “functional” images of blood flow ■ Single Photon Emission Tomography (SPECT) or metabolic processes. They surpass Principle: Distribution of radiopharmaceutical conventional structural or anatomic images administered to patient is measured from many produced by X-ray examination, magnetic different anagles by a rotating gamma camera resonance imaging, and even SPECT. head. Application: Main interest in heart ■ Rectilinear Scanning perfusion imaging and brain imaging. Principle: Moving detectors that map the location Examination of liver and spine also is frequent of radiopharmaceuticals in a patient’s body. clinical application. Comparative Advantage: Scanner moves across the organ in one or more Improved gamma camera imaging. Permits planes until the organ or the area under absolute three-dimensional localization of examination has been completely surveyed by the radiopharmaceutical distribution with 3-D scintillation counter. Application: Thyroid representation of the imaged organ. imaging. Comparative Advantage: Thick crystals ■ Positron Emission Tomography (PET) and high-energy collimation provide high Principle: When a postron combines with an efficiency and resolution, particularly with electron, the action produces two 511-keV radiopharmaceuticals such as iodine-131. annihilation photons moving in opposite ■ General Gamma Probes directions. By recording their simultaneous arrival Principle: The activity of a radiopharmaceutical is 38 in a detector system surrounding the patient, the detected using a collimated scintillation probe origin of the emission can be located in three detector aligned with the organ under dimensions, resulting in extremely high-quality examination. Application: Thyroid uptake of images. Basic organic elements, such as carbon- iodine. Single probe counting systems that 11, nitrogen-13, oxygen-15, and fluorine-18 are employ only one crystalline detector are useful. positron emitters. These elements are tagged to Comparative Advantage: Thyroid uptake as an common molecules found in the body and index of thyroid function remains a routine therefore can be made specifically for a target diagnostic took, even though more sophisticated organ. Application: By combining a positron procedures are available.

and neck are being treated with “conformal therapy”. components to a conventional less extensive surgery Stereotactic radiosurgery (single linear accelerator. The use has combined with radiotherapy. fraction) and stereotactic rapidly expanded for smaller, Easily damaged organs such as radiotherapy (multiple fractions) often benign lesions within the the eye, brain or spinal cord are developments of this brain where surgery is hazardous. can be accurately distinguished conformal therapy. But they Typically arterio-venous from the tumour. place an emphasis on tumour malformations, acoustic Emerging Directions. positioning. schwannomas and meningiomas Sophisticated planning systems While these techniques were of the brain are well managed now design each treatment beam initially developed for proton with this technique, with control to minimize dose to these accelerator beams or a gamma rates exceeding 80%. structures while escalating the knife (a very elaborate ■ Radiotherapy Services. tumour dose. These planning teletherapy unit with over 200 Radiotherapy services have systems control the dose output cobalt sources) this has now expanded rapidly over the last (intensity) and treatment become more generally available decade. The most developed IAEA BULLETIN, 42/1/2000 apertures to deliver so-called with the use of add-on countries make few ■ Surgical Gamma Probes throughout the compartment being studied, and Principle: A hand-held surgical detector is used whose distribution can be traced. Application: to detect and survey the positive accumulation Measures with great accuracy total body water, of a radiopharmaceutical that is administered red blood cell mass, survival and sequestration, before surgery. Application: Allows surgeon to total exchangeable potassium. Tritiated water is identify the first lymph node downstream from a generally preferred for body water determinations. tumour, usually melanoma or a breast tumour. Chromium-51 sodium chromate is used for Comparative Advantage: Improves effectiveness labelling red blood cells. Comparative Advantage: of surgical treatment, which invariably depends Measurement is simple and accurate. upon the complete removal of all tumour tissue. Radionuclides used are not toxic. The metastasis of melanoma or breast cancer will ■ Therapeutic Applications pass down the lymph system and deposit some Principle: Radiotherapy of cancer involves the cells in the first or “sentinel” lymph node. By targeting of radioactivity to tumour cells rather localization of this node, the spread or lack of than the cells of normal tissues. Beta or alpha cancer cells can be identified and appropriate emitting radionuclides can be labelled to some treatment can be applied to the patient. compounds which deliver radiation with cellular ■ Radionuclide Clearance Studies damaging effect to local tissue, where it Principle: Basically, the rate at which a particular accumulates. Selective uptake in particular radioactive substance, usually administered to tumours or organs occurs with these radionuclides patients intraveneously, is cleared from the plasma or labelled compounds. Application: Many can be detemined by calculating the different radiopharmaceuticals that seek out concentration of the substance in plasma and/or tumours are being used for therapy by different urine. Application: Studies offer the ability to routes and a variety of targeting mechanisms. do combined examinations of renal function and Treatment of thyroid cancer or hyperthyroidism anatomy. Comparative Advantage: Radionuclide with iodine-131 has been used for more than 50 Clearance Studies reflect much more precisely years. Some radiopharmaceuticals selectively 39 the functional state of kidneys. Conventional accumulate in metastatic sites of bone tissue chemical analysis tends to be diagnostic in which enables the management of pain. applications for severe renal cases and therefore Comparative Advantage: Treatment specifically inadequate for patients with only moderate loss of targets tissues, is non-invasive, and holds relatively renal function. little early and late side effects. Tracer studies ■ Radionuclide Dilution Techniques further enable assessment of the uptake and Principle: Techniques involve the administration retention of radiation in the tumour before to the patient of a radionuclide that diffuses treatment begins. compromises in accessibility of amount of equipment available Emerging Directions. A new basic radiation oncology for use. Of the IAEA’s 130 challenge presented to services. They have centres Member States, only 10 of the radiation oncologists is the where the highest level of least developed countries now increasing number of cancers technology can be applied, lack basic radiotherapy associated with AIDS seen in when necessary. Though high technology. The IAEA initiated the clinics. The role of technology techniques are only radiotherapy in five of these radiotherapy remains in the required for a minority of Member States over the past control of these cancers but the patients, their use can result in five years. The sixth is objectives of treatment have a major improvement in currently being established. undergone radical revision. control or reduction of The challenge for the next No longer is cancer cure, morbidity in appropriately decade will be to raise the obtainable in about 45% of selected patients. standards to levels where the patients in developed Developing countries over best modern techniques can countries, the prime objective. the last decade show a safely be incorporated into Quality of life issues, always of threefold increase in the their treatment practice. importance to the patient and IAEA BULLETIN, 42/1/2000 RADIOTHERAPY CENTRES & UNITS WORLDWIDE REGION POPULATION RADIOTHERAPY COBALT-60 CLINICAL TELE TELE- (MILLIONS) CENTRES UNITS ACCELERATORS MACHINES MACHINES (TOTAL) (RATIO*) North America 300.9 1903 207 2251 2458 8.2 Central America 134.1 139 115 30 145 1.1 Tropical South America 276.2 266 219 122 341 1.2 Temperate South America 54.3 139 128 46 174 3.2 Caribbean 29.4 18 23 1 24 0.8 Western Europe 387 1027 410 1109 1519 3.9 Eastern Europe 390.6 334 508 182 690 1.8 Northern Africa 138.2 59 54 41 95 0.7 Central Africa 358.6 22 25 2 27 0.1 Southern Africa 56.5 21 19 27 46 0.8 Middle East 221.3 91 64 56 120 0.5 Indian Subcontinent 1245.1 221 286 46 332 0.3 South East Asia 477.2 81 71 59 130 0.3 East Asia 1430.9 1107 606 948 1554 1.1 Australia & Pacific Islands 22.6 49 5 113 118 5.2 * Average number of tele-machines per million people in region. Source: Directory of Radiotherapy Centres,November 1999.

the treating oncologist, become About 80% of all patients with potential for improving health even more significant when this malignancy receive care in many countries. The faced with a limited life brachytherapy as part of their most widespread diagnostic in expectancy from a more lethal treatment. Cure rates range vivo applications worldwide disease. from 80% in tumours confined remain gamma camera ■ Brachytherapy. Advances to the cervix to 35% in tumours examinations of organ functions. are rapid in this application. at stage III. These may be over Promising applications, The original radium sources of 10 centimeters in size and yet however, are emerging in this Marie Curie have mostly been highly curable using combined field, including PET and new replaced with caesium sources tele- and brachtherapy with classes of radiopharmaceuticals. 40 which are safer to handle and brachytherapy as the major In vitro applications of radio- involve easier disposal. While a component. immunoassay, molecular biology, few millimeters may initially As teletherapy is usually and measurement of stable appear small, the introduction of administered on a daily basis as isotopes by nuclear and related these sources into cavities and an outpatient, the advent of techniques are examples of tissues is difficult. New micro micro high-dose rate therapy highly successful technologies high-dose rate sources under one now has eliminated hospital that are far from being mature, millimeter in diameter and admission during treatment. and hold considerable potential having high activities in the Emerging Directions. for growth. order of 10 Curies have paid Endovascular treatment for the For therapeutic applications, dividends. They have made prevention of coronary artery radiation treatment by procedures for insertion easier, restenosis after bypass surgery or teletherapy and brachytherapy shortened treatment times to dilatation of constricted heart are still the treatments of choice typically 10 to 20 minutes vessels has now brought to be offered to most cancer instead of 2 to 5 days, and brachytherapy into the field of patients. But new developments opened new possibilities. These management of “benign” in conformal therapy and of sources can be directed into diseases by radiation. Results surprisingly effective cancer- small bronchi of the lungs, bile indicate that the significant seeking radiopharmaceuticals for ducts and even small heart restenosis rate may have dropped treatment by open radioactive vessels (coronary arteries). The by a factor of four for different sources seem promising. older brachytherapy units, on surgical interventions. Another exciting development -- the other hand, were almost intravascular treatment of exclusively confined to the REALIZING THE artheroscerosis by radiation -- treatment of the uterine cervix. POTENTIAL may confer a new dimension to Cancer of the cervix remains Advances in the medical the treatment of what is the the most common cancer in application of nuclear number one killer disease in IAEA BULLETIN, 42/1/2000 many developing countries. technologies hold significant the industrialized world. ❑