ASN Report 2018

1 —  Nuclear-based medical activities 1.1  ̶  The different activity categories The nuclear-based therapeutic medical activities, particularly those dedicated to the treatment of cancer, include external- beam radiotherapy, brachytherapy and internal targeted radiotherapy. The nuclear-based diagnostic medical activities include computed tomography, conventional radiology, dental radiology and diagnostic nuclear medicine. Interventional practices using ionising radiation (fluoroscopy- guided interventional practices) group together different techniques used primarily for invasive medical or surgical procedures for diagnostic, preventive and/or therapeutic purposes. These different activities and the techniques used are presented in sections 2 to 7. 1.2  ̶  Exposure situations in the medical sector 1.2.1  –  Exposure of health professionals The risks for health professionals arising from the use of ionising radiation are above all the risks of external exposure generated by the medical devices (devices containing radioactive sources, X-ray generators or particle accelerators) or by sealed and unsealed sources (particularly after administering radiopharmaceuticals). When using unsealed sources, the risk of internal 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 2017 by IRSN, 208,921 persons working in the areas of medical and veterinary activities were subject to dosimetric monitoring of their exposure. Radiology activities (radiodiagnosis and interventional radiology) account for the largest proportion of exposed medical personnel (36%). Nearly 99% of the health professionals monitored in 2017 received an annual effective dose below 1 millisievert (mSv). One exceedance of the annual effective dose limit of 20 mSv was observed in a hospital porter who worked in several departments (total annual effective dose of 43.7 mSv). Four cases in which the annual equivalent dose at the extremities (500 mSv) was exceeded were registered in 2017, all in the radiology sector. The average annual individual dose for people having received a dose exceeding the registration threshold is 0.29 mSv/year, slightly down on the value for 2016. In 2017, the very large majority of routine internal exposure monitoring was carried out by radiotoxicological analyses of urine and whole-body radiation measurement examinations (less than 5% of exposed medical professionals); 1,392 people underwent routine monitoring by radiotoxicological analyses of urine. The majority of these analyses concern workers in the nuclear medicine sector. Only one worker underwent a committed effective dose calculation in 2017, and the dose was below 0.1 mSv. 1.2.2  –  Exposure of patients The patient’s exposure situation differs depending on whether diagnostic or therapeutic medical applications are being considered. In the first case, it is necessary to optimise the exposure to ionising radiation in order to deliver the minimum dose required to obtain the appropriate diagnostic information or to perform the planned interventional procedure; in the second case, it is necessary to deliver the highest possible dose needed to destroy the tumoral cells while at the same time preserving the healthy neighbouring tissues to the best possible extent. Whatever the case however, control of the doses delivered during imaging examinations and treatments is a vital requirement that depends not only on the skills of the patient radiation protection professionals but also on the procedures for optimising and maintaining equipment performance. Controlling doses in medical imaging remains a priority for ASN which, following on from the first plan initiated in 2011, published a new opinion along with a second plan in 2018 in order to continue promoting a culture of radiation protection with the professionals (see chapter 1). 1.2.3  –  Exposure of the public With the exception of incident situations, the potential impact of medical applications of ionising radiation is likely to concern: ∙ ∙ members of the public who are close to facilities that emit ionising radiation but do not have the required protection; ∙ ∙ persons close to patients having received a nuclear medicine treatment or examination, involving in particular radionuclides such as iodine-131, or brachytherapy using iodine-125; ∙ ∙ the specific professional categories likely to be exposed to effluents or wastes produced by nuclear medicine departments. CHAPTER 07 F or 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. The benefits and usefulness of these techniques have long been proven, but they nevertheless contribute significantly to the exposure of the population to ionising radiation. They effectively represent the second source of exposure for the population (behind exposure to natural ionising radiation) and the leading source of artificial exposure (see chapter 1). Medical uses of ionising radiation 202  ASN report on the state of nuclear safety and radiation protection in France in 2018