extremities. The radiology sector has the largest number of monitored workers, with about 68% of the total headcount of medical personnel monitored by dosimetry at the extremities (47% for interventional radiology and 21% for diagnostic radiology), and represents 29% of the total exposure dose to the extremities in the medical field. The nuclear medicine sector represents 19% of the monitored personnel and accounts for 68% of the total dose in this area. One hundred and thirty-eight workers in the dental sector are subject to dosimetry monitoring at the extremities and represent less than 0.1% of the total dose to the extremities. 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. Lastly, nearly 87% of the personnel monitored for exposure to the lens of the eye work in medical activities, representing 5,906 workers accounting for 60% of the total dose to the lens of the eye. The average individual dose for medical activities in 2022 was 1.59 mSv. Nearly two-thirds of the personnel monitored for lens of the eye dosimetry work in the FGIP sector which accounts for 60% of the total dose in the medical sector. Under the noteworthy events of 2022, a nuclear medicine worker received a dose to the lens of the eye of between 20 mSv and 50 mSv, with a cumulative five-year dose exceeding 100 mSv which, for the transient 2018-2023 period provided for by the regulations, exceeds the regulatory limit. 1.2.2 Exposure of patients In medical applications for diagnostic purposes, optimisation of exposure to ionising radiation allows delivery of the minimum dose that produces the relevant diagnostic information or allows performance of the planned interventional procedure. For therapeutic applications, the dose delivered must be much higher than in diagnostic applications in order to destroy the targeted cells while preserving the surrounding healthy tissue as best possible. As the principle of limitation does not apply to patients, the principles of justification and optimisation (see point 1.3) must be applied all the more rigorously. In medical imaging, the principles of optimisation and justification (avoiding unnecessary examinations, or those whose result can be obtained using non-irradiating techniques that give an equivalent diagnostic level when available) are at the centre of the action plans for controlling doses delivered to patients. These action plans were developed by the French Nuclear Safety Authority (ASN) in 2011 and 2018 in collaboration with the services of the Ministry of Solidarity and Health and the health professionals. The action plan of 2018 will be updated after finalising the situation assessment carried out in 2024 with all the stakeholders. The optimisation principle, defined by Article L. 1333‑2 of the Public Health Code (see chapter 2), known as the ALARA(2) principle, has led to the introduction, in the area of medical imaging using ionising radiation, of the concept of “Diagnostic Reference Levels” (DRLs). These DRLs, which must not be considered to be “dose limits” or “optimum doses”, are established for standard examinations and typical patients. The DRLs are thus dosimetric indicators of the quality of practices. The comparison of a DRL value with a dose received during an individual examination is not relevant for a given individual, 2. The “As Low As Reasonably Achievable” (ALARA) principle appeared for the first time in Publication 26 of the International Commission on Radiological Protection (ICRP) in 1977. It was the result of a process of reflection on the principle of optimising radiological protection. Over the past thirty years, the acceptance and implementation of the ALARA principle has developed significantly in Europe, with strong backing from the European Commission, leading in 1991 to the creation of a European ALARA network. because in certain situations the conditions of the examination can explain a higher value (to take into account the patient’s morphology for example, or other factors that do not call into question the benefit/risk of the procedure). The optimisation principle should lead the persons/entities Responsible for a Nuclear Activity (RNA) that uses imaging by ionising radiation to compile their own Local Dose Reference Levels (LDRLs) to continue optimising their practices if this is compatible with obtaining a diagnostic quality image. ASN encourages such practices and wants the medical professionals to generalise them in the interest of the patients. ASN resolution 2019-DC-0667 of 18 April 2019 sets the DRL values and requires heads of radiology and nuclear medicine departments to carry out (or have others carry out) periodic dosimetric evaluations and to send the results to IRSN. The data collected by IRSN are analysed with a view to updating the DRLs. In 2023, ASN asked IRSN and then the Advisory Committee of Experts for Radiation Protection (GPRP – see chapter 2) to produce new DRL values for Digital Radiography (DR) mammography and tomosynthesis (3D) mammography. ASN will update the above-mentioned resolution in 2024 on the basis of these new values. The last “ExPRI” study, which analyses exposure of the French population to ionising radiation due to medical imaging examinations, was published by IRSN in late 2020. It presents the data for 2017, which are compared with those of 2012 to show how they have evolved. These analyses are carried out using diagnostic imaging procedures drawn from a representative sample of beneficiaries of the French health insurance system, by method of imaging (conventional, interventional and dental radiology, CT scans and nuclear medicine), by explored anatomical region, by age and by sex. The analyses reveal stability of exposure on average (see chapter 1, point 3.3). 1.2.3 Exposure of the public The impact of medical applications of ionising radiation is likely to concern: ∙ members of the public who live near facilities that emit ionising radiation and the persons working in these facilities who are not workers classified in application of the Labour Code with regard to the radiological risk; ∙ embryos or foetuses exposed in utero during a radiological or nuclear medicine examination of pregnant women; ∙ the personnel of the sewage networks and wastewater treatment plants who could be exposed to effluents produced by nuclear medicine departments, and in the event of non-compliance with waste management procedures, the personnel working in waste treatment facilities who could be exposed to waste produced by nuclear medicine departments or by patients at home having received therapeutic nuclear medicine treatment; ∙ persons supporting and comforting patients having received therapeutic nuclear medicine treatment and healthy volunteers participating in biomedical research involving exposure to ionising radiation; as these exposures enter into the scope of the regulatory obligations applicable to medical exposures, they are not subject to the public dose limits but they must comply with the dose constraints (see point 1.2.3). The estimated doses for the public (people external to the health facility) resulting from discharges from nuclear medicine departments are a few tens of microsieverts (µSv) per year for the most exposed people, primarily the personnel working in sewage networks and wastewater treatment plants (IRSN studies, 2005 ASN Report on the state of nuclear safety and radiation protection in France in 2023 207 • 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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