1. Radiation protection and medical uses of ionising radiation 1. Internal Targeted Radiotherapy (ITR) aims to administer a RadioPharmaceutical Drug (RPD) emitting ionising radiation which will deliver a high dose to a target organ for curative or palliative purposes. 1.1 The different activity categories Medical nuclear activities can be divided into nuclear activities for diagnostic purposes such as computed tomography, conventional radiology, dental radiology and diagnostic nuclear medicine, interventional practices using ionising radiation (FGIPs), which bring together different techniques used primarily for invasive medical or surgical procedures for diagnostic, preventive or therapeutic purposes, and activities for therapeutic purposes, most of which are dedicated to cancer treatment, such as externalbeam radiotherapy, brachytherapy and ITR(1). These different activities and the techniques used are presented in sections 2.1 to 2.6. 1.2 Exposure situations in the medical sector 1.2.1 Exposure of health professionals Medical professionals are subject in particular to the risk of external exposure created by the medical devices (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 data collected in 2021 by Institute for Radiation Protection and Nuclear Safety (IRSN), the medical and veterinary sectors account for the majority of the people monitored: 60%, i.e. 234,284 persons were subject to dosimetric monitoring of their exposure. The average annual individual dose is 0.27 millisievert (mSv). This figure remained relatively stable between 2015‑2021, with the exception of 2020, when it dropped by 17% due to the Covid-19 pandemic. The analysis of the breakdown of the persons according to their level of exposure shows that the very large majority of workers (75% all sectors combined) received no dose above the detection threshold. The largest proportion (48%) of exposed medical personnel is involved in radiology activities (diagnostic radiology and interventional radiology), with an average annual individual dose of 0.20 mSv. Nuclear medicine represents 3% of the personnel but with a significantly higher average annual individual whole body dose, estimated at 0.84 mSv. The medical and veterinary activity sectors account for the majority of exposures of the extremities, with nearly 61% of the workers subject to this monitoring in 2020 and 2021. Altogether, 17,252 people were subject to dosimetry of the extremities, with an average dose of 14.9 mSv compared with 14.7 mSv in 2020. Nuclear medicine and interventional practices are the sectors that make the greatest use of ring dosimeters and contribute the most to exposures of the extremities (68% and 16% respectively of the total dose recorded for the medical and veterinary activity sectors). The contribution of interventional activities to the total dose is probably underestimated, particularly due to insufficient use of extremity dosimeters by staff in the operating theatre. For the first time since 2013, no exceeding of the regulatory limit for the equivalent dose to the extremities (500 mSv) was recorded in the medical sector in 2021. 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 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) and Internal Targeted Radiotherapy (ITR), the major risk is linked to the administered dose and, if applicable, the high dose rates used. There are specific risks linked to the use of sealed radionuclide sources (in brachytherapy, with high-activity sources) and unsealed sources (in nuclear medicine), which bring the risks associated with waste and effluent management. The fast expansion of Fluoroscopy-Guided Interventional Procedures/Practices (FGIPs) carried out using increasingly sophisticated devices can lead to significant exposure of the patient and the 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, 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. 208 ASN Report on the state of nuclear safety and radiation protection in France in 2022 • 07 • Medical uses of ionising radiation
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