LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 2.3.1 – Description of the techniques In vivo diagnostic nuclear medicine provides functional imaging. This technique consists in examining a function of the organism by administering a specific radioactive substance – an 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 threedimensional reconstruction of the organs. Depending on the type of radionuclide used, the term SPECT, still called “gamma-camera”, 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 labelled with iodine-125), hence the name Radio Immunology Assay or radioimmunoassay – RIA). However, the number of in vitro diagnostic laboratories has been decreasing for several years due to the use of more effective non-ionising techniques, 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. Nuclear medicine has two distinct therapeutic applications: oncology and non-oncology. 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. This research is leading to the gradual introduction of new treatments which are intended to be proposed to a growing number of patients in the coming years, raising radiation protection issues which are currently being examined by ASNR. ITR treatments can be administered either by mouth (e.g. capsule of iodine-131) or by systemic route (intravenous injection or via a catheter). Some treatments – depending on the administered activity or the nature of the radionuclide and the RPD used – require patients to be hospitalised for several days in specially fitted-out rooms in the nuclear medicine department to ensure the radiation protection of the personnel, of people visiting the patients and of the environment. The radiological protection of these rooms is adapted to the nature of the radiation emitted by the radionuclides, and the contaminated urine of the patients is collected in tanks. When treatments are administered on an out-patient basis or in hospital rooms external to the nuclear medicine department, a circuit must also be provided to channel the patients’ urine to decay tanks, knowing that ASN’s circular letter of 12 June 2020 provides for, in the case of treatments based on lutetium-177, provisional derogation measures to give departments without these tanks time to install them. Out-patient treatment also implies, in certain cases, decay management of the waste produced by the patients in their home prior to disposal via the household waste route. Forty-six nuclear medicine departments have a combined total of 172 ITR rooms for therapeutic purposes (see Graph 5). New RPDs for therapeutic or diagnostic purposes continue to be developed, requiring numerous clinical research projects in nuclear medicine, involving actinium-225, lead-212 and astatine-211, among others. This research may also involve Medical Devices (MDs) or Active Implantable Medical Devices (AIMDs), such as holmium-166 microspheres. The regulations require any sponsor of a clinical trial to obtain a favourable opinion from a Research Ethics Committee (CPP) and authorisation from ANSM before commencing the clinical trial. Research involving health products containing radioactive sources may only be conducted once the authorisations issued by ASNR (Article R. 1333-118 of the Public Health Code) in addition to the CPP opinion and, where applicable, ANSM authorisation, have been obtained. Until now, ASNR only issued authorisation for the use of a radionuclide once ANSM had granted license for the clinical trial. To facilitate the inclusion of centres in clinical trials, ASNR launched a pilot scheme at the end of September 2025 for the early granting of authorisations for the possession and use of radionuclides. A first early authorisation was granted by ASNR’s Lyon division to the Hospices Civils de Lyon for the implementation of a trial protocol using actinium-225. Medical dispensaries On account of the ongoing reform of healthcare authorisations (see point 2.3), the authorisation for level A holders requires that a radiopharmacist be attached to the medical dispensary if the nuclear medicine department is located in a site that has a dispensary. For the holders of level B, the radiopharmacist duties are ensured and 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 TABLE 3 Main radionuclides used in diverse in vivo nuclear medicine explorations ASNR Report on the state of nuclear safety and radiation protection in France in 2025 207 01 05 02 03 04 09 06 10 07 11 13 08 12 A / Z
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