If the dose delivered does not in itself represent a radiation protection health risk, it is the large number of examinations carried out among the population that contributes significantly to the collective dose of medical origin. 2.5.1.1 Medical radiodiagnosis Conventional radiology Conventional radiology (producing radiographic images), 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 (arteriography) or venous (venography) tree 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 detail required, screening for breast cancer necessitates the use of mammography units, specific radiology devices providing high-definition and high-contrast images. Two complementary imaging techniques are currently available, planar imaging (2D) and tomosynthesis imaging (3D). Only planar imaging, which functions at low voltage and offers high definition and high contrast, is at present approved by the HAS for breast cancer screening. ASN participates in a working group coordinated by the HAS which is assessing the position of tomosynthesis mammography in the breast cancer screening strategy. In 2019, the HAS published a first report on the technical performance of tomosynthesis mammography in breast cancer screening of average-risk women. A second report on the evaluation of the performance and the position of tomosynthesis mammography in the French organised breast cancer screening programme should be published in 2023. The use of these devices is subject to quality controls defined by the ANSM. The planar imaging (2D) quality controls are defined by the ANSM resolution of 15 January 2020 which entered into effect on 15 January 2021. ASN was consulted in this context and gave a favourable opinion on the draft resolution relative to the internal and external quality controls of digital mammography facilities. This resolution is currently being updated. The future resolution will update the checks performed on 2D mammography units and will introduce EQCs for the tomosynthesis devices. Computed tomography Computed tomography (CT) scanners use a beam of X-rays emitted by a tube which moves in a spiral around the body of the patient (helical CT scanner). These scanners produce a threedimensional reconstruction of the organs with very much better image quality than that of conventional radiology devices. The number of rows of detectors (multidetector-row CT scanner, also known as a multislice or volumetry CT scanner) has been increased in recent machines, enabling thinner slices to be produced. An examination can comprise several helical image acquisitions of a specific anatomical region (with or without injection of a contrasting agent) or of different anatomical regions. 9. The term indication means a clinical sign, an illness or a situation affecting a patient which justifies the value of a medical treatment or a medical examination. This technique can, like MRI, be associated with functional imaging provided by nuclear medicine in order to obtain fusion images combining functional information with structural information. The technologies developed over the last few years have made examinations easier and faster to perform, and have led to an increase in exploration possibilities (example of dynamic volume acquisitions) and in the indications(9).The placing of mobile CT systems on the market for intraoperative use is to be underlined, as is the increase in fluoroscopy-guided interventional CT procedures. ASN notes the emerging trend to equip ambulances with CT scanners in order to perform CT scans on stroke patients. On the other hand, these technological developments have led to an increase in the number of examinations, resulting in an increase in the doses delivered to patients and thus reinforcing the need for strict application of the principles of justification and optimisation (see point 1.3.4). Technical progress has nevertheless brought a new mode of image reconstruction in the form of iterative reconstruction. Computed tomography can thus provide consistent image quality at reduced doses. The devices can also be equipped with dose-reduction tools. Teleradiology Teleradiology provides the possibility of performing and remotely interpreting radiological examinations. The interchanges must be carried out in strict application of the regulations (relating to radiation protection and the quality of image production and transfer in particular) and professional ethics. Essentially two interchange methods are used: ∙ Telediagnosis, which enables a doctor on the scene (e.g. an emergency doctor), who is not a radiologist, to perform the radiological examination and then send the results to a radiologist in order to obtain an interpretation of the images. If necessary the radiologist can guide the radiological operator during the examination and imaging process. In this case, the doctor on the scene is considered to be the doctor performing the procedure and assumes responsibility for it. ∙ Tele-expertise, which is an exchange of opinions between two radiologists, where one asks the other – the “expert radiologist” (teleradiologist) – for a remote confirmation or contradiction of a diagnosis, to determine a therapeutic orientation or to guide a remote examination. The data transmissions are protected and preserve medical secrecy and image quality. Teleradiology involves multiple responsibilities, which must be specified in the agreement binding the doctor performing the procedure to the teleradiologist. The teleradiology procedure is a medical procedure in its own right, like all other imaging procedures, and cannot be reduced to a simple remote interpretation of images. Teleradiology therefore fits into the general healthcare organisation governed by the Public Health Code and obeys the rules of professional ethics in effect. The Teleradiology Charter published by the French professional council of radiology (G4) was re-updated in 2020. It details the organisation of the two parts of teleradiology (telediagnosis and tele-expertise). In addition, a guide to good practices concerning the quality and safety of teleimaging procedures was published in May 2019 by the HAS. In this guide the HAS makes important clarifications concerning the proper use of “medical imaging examinations with remote interpretation”. It has the particularity of also addressing nuclear telemedicine, deployed with the aim of providing uniform coverage across the country. This guide does not consider mammography, which cannot be done by ASN Report on the state of nuclear safety and radiation protection in France in 2022 231 • 07 • Medical uses of ionising radiation 07 01 08 13 AP 04 10 06 12 14 03 09 05 11 02
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