ASN Report 2018

regulatory limit was exceeded in just one of these cases, and this ESR was rated level 1 on the INES scale. The centre concerned was inspected in early 2019. The other cases concern exposures of dosimeters lost by the personnel, one case concerns intentional exposure of a dosimeter to test the operation of a mobile C-arm, while others concern active dosimetry malfunctions. SUMMARY In the areas of fluoroscopy-guided interventional practices, ASN considers that the urgent measures it has been recommending for several years to improve the radiation protection of patients and professionals in the exercise of interventional practices have still not been sufficiently implemented, particularly for surgical procedures performed in operating theatres. The inspections frequently reveal deviations from the regulations, concerning the radiation protection of patients as much as of medical staff, and ASN is regularly notified of events concerning interventional practitioners who have exceeded the dose limits for the extremities. The radiation protection situation is however significantly better in the departments that have been using these technologies for a long time, such as the imaging departments performing interventional cardiology and neurology activities. Substantial awareness-raising in all the professionals is necessary to help the medical, paramedical and administrative staff of the medical centres gain a better perception of the risks, particularly for the professionals working in operating theatres. In ASN’s opinion, the continuous training of the professionals and the involvement of the medical physicist probably constitute the two key points to guarantee the doses delivered to patients during interventional procedures. 6 —  Medical and dental radiodiagnosis 6.1  ̶  Overview of the equipment Medical diagnostic radiology is based on the principle of differential attenuation of X-rays by the organs and tissues of the human body. The information is collected on digital media allowing computer processing of the resulting images, and their transfer and filing. Diagnostic X-ray imaging is one of the oldest medical applications of ionising radiation; it encompasses all the methods of morphological exploration of the human body using X-rays produced by electric generators. It occupies an important place in the field of medical imaging and comprises various techniques (conventional radiology, radiology associated with interventional practices, computed tomography, mammography) and a very wide variety of examinations (radiography of the thorax, chest-abdomen-pelvis computed tomography scan, etc.). The request for a radiological examination by the physician must be part of a diagnostic strategy taking account of the patient’s known medical history, the question posed, the expected benefit for the patient, the examination exposure level and the dose history and the possibilities offered by other non-irradiating investigative techniques. A guide intended for general practitioners ( Guide to good medical imaging examination practices ) indicates the most appropriate examinations to request according to the clinical situations (see box on next page). 6.1.1  –  Medical radiodiagnosis • Conventional radiology Conventional radiology (producing radiographic images, or radiographs), if considered by the number of procedures, represents the large majority of radiological examinations performed. The examinations mainly concern the bones, the thorax and the abdomen. Conventional radiology can be carried out in fixed facilities reserved for diagnostic radiology or, in certain cases, using portable devices if justified by the clinical situation of the patient. • Angiography This technique, used for exploring blood vessels, involves injecting a radio-opaque contrast agent into the vessels which enables the arterial tree (arteriography) or venous tree (venography) to be visualised. Angiography techniques benefit from computerised image processing (such as digital subtraction angiography). • Mammography Given the composition of the mammary gland and the fineness of the details required in order to make a diagnosis, specific devices (mammography units) are used. They operate at low voltage and provide high resolution and high contrast. They are used in particular in the national breast cancer screening programme. Overexposure of a female patient when performing a biopsy with CT guidance The patient was exposed to a high dose of ionising radiation that could have subsequent consequences on her health, according to the expert assessment requested of IRSN. The inspection showed that the complexity of the procedure necessitates a particular image reconstruction technique and that the CT scanner used did not integrate the latest developments for optimising the doses delivered to patients. Furthermore, a number of organisational malfunctions led to the failure to prevent the occurrence of this event (lack of knowledge and training of the personnel, poor communication within the teams, constraints linked to the work environment). ASN subsequently limited the license of this hospital’s CT scanner to diagnostic procedures. 224  ASN report on the state of nuclear safety and radiation protection in France in 2018 07 – MEDICAL USES OF IONISING RADIATION