LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT For more than a century now, medicine has made use of ionising radiation produced either by electric generators or by radionuclides in sealed or unsealed sources for both diagnostic and therapeutic purposes. These techniques represent the second source of exposure of the population to ionising radiation (behind exposure to natural ionising radiation) and the leading source of artificial exposure (see chapter 1). The exposure of patients to ionising radiation for diagnostic or therapeutic purposes is distinguished from the exposure of workers, the public and the environment, for which there is no direct benefit. The principle of dose limitation does not apply to patients due to the need to adapt the delivered dose to the diagnostic or therapeutic end-purpose. The principles of justification and optimisation are fundamental, even if the radiation protection risks differ according to the medical uses. In radiotherapy (external-beam or brachytherapy) as in Internal Targeted Radiotherapy (ITR) which is developing strongly at present, the major risk is linked to the administered dose and, if applicable, the high dose rates used. The use of high-activity sealed radioactive sources in brachytherapy and unsealed sources in nuclear medicine poses specific challenges for patients. The use of unsealed sources presents risks for the personnel who handle them, for the environment with the management of waste and effluents, and for the carers and comforters. Fluoroscopy-guided interventional practices, whose use continues to increase and which are performed using increasingly sophisticated devices, enable less invasive procedures and the treatment of new indications, but can result in can lead to significant exposure of the patient and personnel in the immediate vicinity. Lastly, Computed Tomography (CT) examinations, although they do not present a major risk in terms of delivered dose or dose rate for an individual, contribute very significantly to population exposure resulting from medical diagnostic procedures due to their frequency of use, underlining the importance of justification for each procedure using ionising radiation. 1 – Radiation protection and medical uses of ionising radiation 1. Internal Targeted Radiotherapy involves administering a RadioPharmaceutical Drug (RPD) or implanting a radioactive medical device so that the ionising radiation delivers a high dose as close as possible to the organ that needs to be treated (also known as the "target organ") for curative or palliative purposes. The majority of these treatments are dispensed within nuclear medicine departments. 1.1 The different activity categories Medical nuclear activities can be divided into two broad categories, namely those for diagnostic purposes and those for therapeutic purposes. The diagnostic medical activities using ionising radiation are diagnostic nuclear medicine and radiology (conventional radiology, computed tomography and dental radiology). Situated at the boundary between diagnostic and therapeutic activities are the Fluoroscopy-Guided Interventional Practices (FGIPs), which bring together various techniques used essentially for invasive medical or surgical procedures carried out for diagnostic, preventive or therapeutic purposes guided via an image obtained using X-rays. The majority of therapeutic activities such as externalbeam radiotherapy, radiosurgery, brachytherapy and therapeutic nuclear medicine (called “Internal Targeted Radiotherapy” – ITR(1)) are devoted to the treatment of cancers. These different activities and the techniques used are presented in points 2.1 to 2.6. 1.2 Exposure situations in the medical sector 1.2.1 – Occupational exposure Medical professionals are subject in particular to the risk of external exposure created by the Medical Devices (MDs – devices containing radioactive sources, X-ray generators or particle accelerators) or by sealed or unsealed sources. When using unsealed sources, the risk of contamination must also be taken into consideration in the risk assessment (in nuclear medicine and in the biology laboratory). According to the latest available data, collected in 2024 by the Authority for Nuclear Safety and Radiation Protection (ASNR), the medical field accounts for the majority of personnel subject to individual dosimetric monitoring: 43% of all classified workers, i.e. 106,426 people, were monitored. The personnel headcount has dropped by nearly 13% overall compared with 2023. This drop is mainly due to the fact that the transfer of dosimetric results in the Ionising radiation exposure monitoring information system (SISERI) by accredited organisations is not yet complete. The average 190 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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