Nuclear medicine uses radioactive substances, called radiopharmaceuticals, in the diagnosis and treatment of a range of diseases. These substances are chosen or especially developed to be taken up predominantly by one organ or one type of cell in the body. Nuclear medicine offers unique diagnostic information in oncology, cardiology, endocrinology, neurology, nephrology, urology and other areas. Such information is not obtainable, or obtainable only with less accuracy, by other modalities. For nuclear medicine diagnostic procedures, trace amounts of radiopharmaceuticals are administered to patients through injection into veins (intravenous), skin (intradermal) or tissues (intraparenchymal) as well as breathing in (inhalation) or eating/drinking (ingestion). After intake, the function, or physiology, of various tissues, organs or organ systems can be demonstrated. For example, in cancer patients, nuclear medicine imaging can be used for diagnosis (i.e. is a cancer present), staging (i.e. how far has it spread), assessment of response to therapy or of possible disease recurrence. Nuclear medicine cameras are now commonly combined with a CT unit (e.g. hybrid SPECT/CT and PET/CT) which allows precise anatomic localisation of pathology. (Figure 1, Figure 2a, 2b)
Nuclear medicine procedures for treatment are non-invasive and present no risk of direct complications to patients, but limited to several well-established situations where killing hyperfunctioning or malignant cells is important (for example hyperthyroidism, cancer of the thyroid, degenerative and inflammatory diseases of joints, palliative treatment of metastases to the skeleton). In addition, there are many studies showing significant potential for radio-labelled antibodies and receptor-avid peptides to be used in the treatment of several malignancies.
A patient undergoing nuclear medicine imaging or treatment becomes a radiation source and remains “radioactive” after the radiopharmaceutical has been administered. Radiation protection advice depends on the specific radioisotope and its radiopharmaceutical form administered and whether the procedure is diagnostic or therapeutic. However, the general principles of the ICRP system of radiological protection apply in nuclear medicine as they do for other medical imaging modalities using ionising radiation. In addition ICRP Publication 52 Protection of the Patient in Nuclear Medicine (and Statement from the 1987 Como Meeting of ICRP) and ICRP Publication 94 Release of Patients after Therapy with Unsealed Radionuclides provide recommendations and guidance on the protection and release of patients after therapy with unsealed radionuclides (e.g. post 131 Iodine therapy for thyroid cancer), and ICRP Publication 128 Radiation Dose to Patients from Radiopharmaceuticals: A Compendium of Current Information Related to Frequently Used Substances provides dose coefficients to patients from radiopharmaceuticals.