Nuclear Applications in Health Care Lasting Benefits by Steffen Groth
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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