ASN defines the new methods for evaluating ionising radiation doses delivered to patients for medical imaging procedures and updates the corresponding diagnostic reference levels (DRL)

In a resolution dated 18 April 2019, ASN updates and clarifies the methods for evaluating the ionising radiation doses delivered to patients during medical imaging procedures, in order to help control these doses.

In France, exposure for medical purposes is the leading source of artificial exposure of the population to ionising radiation. This exposure is increasing, mainly due to the greater number of examinations using computed tomography (CT) scanners. In addition, the number of fluoroscopy-guided procedures and their complexity have increased significantly in recent years. These procedures can entail high levels of exposure for the patient.

The DRL are used by professionals to optimise the ionising radiation doses delivered to the patients, in order to reduce exposure, while preserving the quality of the images obtained in order to achieve the desired clinical objective. The DRL are not dose limit values: they enable the professionals to evaluate their practices by comparison with these reference values. These values, set out in an ASN regulation, need to be regularly updated to take account of changing practices and technologies. These levels are defined for the most common practices, but also for those entailing the highest level of exposure.

ASN resolution 2019-DC-0667 of 18 April 2019 updates the diagnostic reference levels (DRL) for dental and conventional radiology, computed tomography and nuclear medicine procedures. For the first time, DRL have also been defined for certain fluoroscopy-guided interventional practices.

This resolution requires that the party responsible for the nuclear activity carry out dosimetric evaluations in paediatrics in addition to those hitherto performed on adults. It specifies how the data are collected, confirms the need to analyse the dosimetry values collected, in order to optimise the doses delivered to the patients and recalls the obligation to send the data thus collected and analysed to IRSN. When the DRL are exceeded, with the exception of justified special situations, the party performing the procedures takes the necessary action to reinforce optimisation.

The ASN resolution also for the first time introduces the notion of a diagnostic guideline value, which is lower than the DRL for the same procedure. The professionals are asked to make efforts to comply with this value as closely as they can, when a more thorough approach to optimising the doses delivered to the patients is possible, without impairing the quality of the images obtained, in order to achieve the desired clinical objective.

ASN resolution 2019-DC-0667 of 18 April 2019 concerning the methods for evaluating ionising radiation doses delivered to patients during a radiology procedure, fluoroscopy-guided interventional or nuclear medicine practices, and the updating of the corresponding diagnostic reference levels, was approved by Order of the Minister responsible for Health of 2 May 2019 and published in the Official Journal of the French Republic. It entered into force on 1 July 2019.

The public and stakeholders were consulted concerning the draft resolution at the end of 2018. Further to the comments received, ASN clarified certain aspects of the text. A summary of the comments received during this consultation is available via the link below.