Controlling and monitoring exposure to radiation from medical imaging.

Above a certain threshold dose, ionising radiation invariably provokes harmful effects such as burns, nausea and aplasia. Their severity increases with the dose received. There is no known threshold dose below which long-term harmful effects, such as cancer and genetic defects, do not occur. Ionising radiation comes from both natural and man-made sources. Worldwide, medical exposure accounts for 98% of the dose received from man-made sources. In France, the average dose per person received from diagnostic radiological examinations increased by more than 50% between 2002 and 2007. This increase was due to more frequent use of computed tomography (CT) and diagnostic nuclear medicine procedures. The internationally defined individual dose limits for the general population do not apply to the medical uses of ionising radiation, but medical exposure must comply with the principles of radiation protection: the examination must be justified and the dose optimised. In France, shortcomings are observed in the application of these principles. In 2012, the French Nuclear Safety Authority (ASN) received 345 reports of "significant radiation protection incidents" affecting patients: 75% involving external beam radiotherapy, 15% involving nuclear medicine, 6% involving CT scans, and 4% involving radiology. In 2011, reference levels were established for the doses received by children during CT imaging and nuclear medicine procedures. When deciding whether to order a diagnostic procedure using ionising radiation, the harm-benefit balance of both the procedure and the chosen technique must be taken into account. When two procedures have the same performance, the technique that exposes the patient to the lowest dose of radiation should be chosen.