ASN Report 2020

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 inject­ ing 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 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. ASN was consulted and gave a favourable opinion on the draft resolution relative to the internal and external quality controls of digital mammography facilities. This resolution updates the checks performed on 2D mammography units and provides for third-party quality controls on the tomosynthesis devices. Tomosynthesis is a new three-dimensional breast imaging technique that is developing in Europe without any form of quality control. The evaluations of this technique, currently in progress in several European countries, should enable its advantages compared with the traditional planar technique to be determined. At present, this technique is not validated for use in organised breast cancer screening. ASN participates in a working group, coordinated by the HAS, to assess the position of tomosynthesis mammography in the breast cancer screening strategy. 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 (spiral or helical CT scanner). Based on a computerised image acquisition and processing system, these scanners produce a three-dimensional 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 computed tomography systems on the market for intraoperative use is to be underlined, as is the increase in fluoroscopy-guided interventional CT procedures. 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 chapter 1). 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 guiding the performance and interpreting the results of radiology examinations carried out in another location. 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 methods of interchange 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 radio­ logist 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. Significant events concerning the radiation protection of medical professionals In 2020, three Significant Radiation protection Events (ESR) concerned workers and formed the subject of an incident notice due to exceeding of the regulatory limit for ionising radiation exposure of the extremities or the whole body. ASN rated these events level 1 on the INES scale (international scale of nuclear and radiological events, graded from 0 to 7 in increasing order of severity). These ESRs occurred during infiltrations by practitioners in radiology and during fluoroscopy-guided surgical vertebroplasty procedures. Two of the professionals received an equivalent dose exceeding 500 millisieverts (mSv) on the hands over 12 consecutive months, while the third received an effective cumulative dose exceeding 20 mSv. The exposure of practitioners to ionising radiation during this type of procedure depends on their individual practices, the radiological image acquisition parameters and the use of personal protective equipment. ASN reminds classified workers of the obligation to wear all their dosimeters and the need to send them to the accredited organisation no later than ten days after the term of the wearing period in order to detect abnormal exposure as soon as possible. The medical professionals must also wear their Personal Protective Equipment (PPE) and apply the optimisation of practices when performing fluoroscopy-guided examinations. ASN Report on the state of nuclear safety and radiation protection in France in 2020 233 07 – MEDICAL USES OF IONISING RADIATION 07