2.3 NUCLEAR MEDICINE Nuclear medicine is a medical discipline that uses radionuclides in unsealed sources for diagnostic purposes (functional imaging in vivo or medical biology in vitro) or therapeutic purposes (ITR). Thanks to the increase in new radionuclides and vectors, nuclear medicine has developed strongly over the last few years, for diagnostic and therapeutic purposes alike. Furthermore, the reform of healthcare licences (see point 1.3.3) has introduced two licensing “levels” for nuclear medicine (levels A and B) in application of Decree 2021-1930 concerning the conditions of installation of nuclear medicine departments. Level A concerns the diagnostic or therapeutic activities other than the treatment of cancerous pathologies, carried out by administering RPDs that are ready to use or are prepared using an aseptic process in a closed system. Level B is attributed when the activity includes, in addition to the procedures covered by level 1, the following procedures: ∙ procedures with the administration of an RPD prepared using an aseptic process in an open environment; ∙ diagnostic procedures carried out for explorations of cellular marking of the formed elements of the blood by one or more radionuclides; ∙ therapeutic procedures carried by the administration of active implantable MDs; ∙ therapeutic procedures for cancerous pathologies performed by administering RPDs. The healthcare activity licence for nuclear medicine shall henceforth be granted by geographical site on condition that the provisions concerning the number of Single Photon Emission Computed Tomography (SPECT) and PET devices are observed (see point 2.3.1). The facilities will have to regularise their situation and submit applications to install new devices in already authorised sites or for the creation of new sites with the ARS. The licenses to possess and use a radioactive source or a device emitting ionising radiation issued by ASN shall be updated according to the nature of these changes (change of holder, site, device, sharing of devices, etc.). Nuclear medicine forms part of ASN’s inspection priorities. The main radiation protection risks are linked in particular to the use of unsealed sources, which generate radioactive waste and effluents, and can lead to contaminations. Nuclear medicine is moreover the main contributor to doses at the extremities of professionals in the nuclear sector (see point 1.2.1). During inspections, particular attention is focused on management of the sources, waste and effluents, occupational radiation protection, control of drug dispensing, through quality assurance obligations and the experience feedback process. 2.3.1 Description of the techniques In vivo diagnostic nuclear medicine allows the production of functional imaging which is complementary to the purely morphological imaging obtained by the other imaging techniques. This technique consists in examining a function of the organism by administering a specific radioactive substance called a “RPD” to the patient. The choice of RPD depends on the studied organ or function. The RPD conventionally consists of a radionuclide which can be used alone (in this case the radionuclide constitutes the RPD) or be attached to a vector (molecule, hormone, antibody, etc.). In the latter case, it is the specific attachment of the vector that determines the studied function. Table 3 presents some of the principal radionuclides used in various explorations. It is by detecting the ionising radiation emitted from the radionuclide by using a specific detector that the RPD can be located in the organism and images of the functioning of the explored tissues or organs can be obtained. The majority of detection devices allow tomographic acquisitions and cross-sectional imaging and a three-dimensional reconstruction of the organs. Depending on the type of radionuclide used, the term SPECT, still called “gammacamera”, is used for radionuclides emitting gamma radiation and PET for radionuclides emitting positons. In order to make it easier to merge functional and morphological images, hybrid appliances have been developed. They combine PET cameras or gamma cameras with a CT scanner (PET-CT or SPECT-CT). A PET camera can also be coupled with an MRI scanner, but this is rarer. In vitro diagnostic nuclear medicine is a medical biology technique used to assay certain compounds contained in the biological fluids sampled beforehand from the patient (e.g. hormones, tumoral markers, etc.); it is used frequently because it has the highest detection sensitivity of the techniques using ionising radiation. This technique uses assaying methods based on immunological reactions (reactions between antigens and antibodies marked with iodine-125), hence the name Radio Immunology Assay or radioimmunoassay – RIA). However, the number of in vitro diagnostic laboratories is decreasing due to the use of techniques offering greater detection sensitivity, such as immunoenzymology or chemiluminescence. Nuclear medicine for therapeutic purposes, or ITR, uses the administration of the RPDs to deliver a high dose of ionising radiation to a target organ for curative or palliative purposes. Two areas of therapeutic application of nuclear medicine can be identified: oncology and non-oncological diseases. Human Subject Research (HSR) in nuclear medicine has been particularly dynamic in recent years, primarily in the field of oncology therapy with the emergence of new vectors and radionuclides. TABLE Main radionuclides used in diverse in vivo nuclear medicine explorations TYPE OF EXAMINATION RADIONUCLIDES USED Thyroid metabolism Iodine-123, technetium-99m Myocardial perfusion Rubidium-82, technetium-99m, thallium-201 Lung perfusion Technetium-99m Lung ventilation Krypton-81m, technetium-99m Osteoarticular process Fluorine-18, technetium-99m Renal exploration Technetium-99m Oncology – search for metastases Fluorine-18, gallium-68, technetium-99m Neurology Fluorine-18, technetium-99m 3 ASN Report on the state of nuclear safety and radiation protection in France in 2023 223 • 07 • Medical uses of ionising radiation 07 05 15 08 11 04 14 06 13 AP 03 10 02 09 12 01
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