B. Habib Geryes et al.: Radioprotection 2025, 60( 4), 294 – 296 295
L’ objectif n’ est donc pas de multiplier des études de portée strictement locale, mais de privilégier des travaux plus larges, multicentriques, intégrant la diversité des pratiques et des indications, ou des études sur l’ évolution pluriannuelle des NRD et des méthodes utilisées pour faire évoluer les pratiques locales, permettant ainsi l’ optimisation de l’ exposition des patients.
Diagnostic reference levels in medical imaging: requirements for optimizing patient radiation protection
***
B. Habib Geryes, L. Lebaron-Jacobs, C. Mercat, J. M. Bertho, M. Bourguignon
Comité de rédaction de Radioprotection
Diagnostic reference levels( DRLs) have become, since their introduction by the International Commission on Radiological Protection( ICRP), an essential tool for optimizing patient doses in medical imaging. ICRP Publication 135 clarified the principles for their establishment and use( ICRP, 2017), and the European PIDRL 185 publication( European Commission, 2018) provided specific recommendations for pediatric radiology, taking into account patient variability and the limited data available. The aim is to harmonize studies and enable better comparability between teams. At the European level, after the publication of the Commission’ s Euclid project on DRLs( European Commission, 2021), the European Society of Radiology conducted a survey as part of the EuroSafe Imaging campaign on practices and challenges related to the implementation of DRLs, which remain heterogeneous despite progress in their adoption( Damilakis et al., 2025).
Radioprotection has published numerous articles on DRLs over the past two years, such as those of Kabeer et al., 2024 and Semghouli et al., 2024 on adult CT, Khajmi et al., 2023 on pediatric CT, and Nassar et al., 2023 on mammography. We continue to receive a large number of manuscripts on this topic. We also receive a significant number of manuscripts addressing patient doses for various procedures. However, the establishment of local or regional DRLs alone is not sufficient to improve patient radiation protection.
First, it should be recalled that DRLs can be defined at different levels: local or regional, to monitor and optimize the practices of a single institution or a group of centers, and then at the national level, based on representative multicenter surveys. These surveys must meet clear methodological criteria, particularly in terms of the minimum number of equipment units( 10 to 20 units at the local or regional level) and participating centers( 30 to 50 % of centers at the national level), with a sufficient number of patients per type of examination( minimum 20 patients per weight subgroup), to ensure the robustness and comparability of the data( ICRP, 2017). These numbers may be increased when automated dose collection systems( DACS) are used.
The methodology for defining DRLs is based on two complementary indicators: diagnostic guidance values( DGVs), corresponding to the median of the collected dose distributions and reflecting current practices, and DRLs defined by the 75th percentile of the distributions, used as a reference tool to identify practices that deviate from the majority. In the pediatric field, PIDRL 185 emphasizes the need to stratify DRLs by children weight and recommends a multicenter approach to obtain sufficient samples. ICRP Publication 135 also specifies dose metrics and their units for each modality and, in cases of limited data, recommends the use of dose – weight curves to establish DRLs.
Publications on DRLs also reflect an evolution: after an initial phase focused on the development of local DRLs, often essential to initiate the process in some countries, the scientific community is now moving toward larger multicenter studies, integrating clinical indications and covering several types of examinations and imaging modalities( conventional radiology, fluoroscopy, CT, interventional radiology, nuclear medicine, etc.)( Damilakis et al., 2025: El Fahssi et al., 2024: Hakme et al., 2023). This dynamic enhances the relevance and usefulness of DRLs for optimization. Furthermore, a growing interest in recent publications lies in considering clinical indications: the same type of examination can indeed be performed according to different protocols and diagnostic objectives, justifying the refinement of DRLs by indication( Habib Geryes et al., 2019).
The optimization process should be understood as a two-step process: first, the establishment of DRLs from representative multicenter collections, and then their adoption and use by each center, which compares its own medians to the DGVs and national DRLs to identify potential margins for optimization. It is this step of optimizing local practices in light of pre-established references that improves patient radiation protection.
Finally, one point deserves emphasis: the use of DGVs and DRLs has made it possible to identify and reduce the most nonoptimized practices. However, the question now arises as to the margins for further improvement: beyond a certain threshold, reducing doses risks compromising image quality and thus diagnostic value. This is the challenge of the next step: to evolve the reflection toward DRLs that integrate both dose and diagnostic information, taking into account real clinical practices.
The objective, therefore, is not to multiply studies of strictly local scope, but to prioritize broader, multicenter studies that integrate the diversity of practices and indications, or studies on the multi-year evolution of DRLs and the methods used to improve local practices, thereby enabling the optimization of patient exposure.
B. Habib Geryes, L. Lebaron-Jacobs, C. Mercat, J. M. Bertho and M. Bourguignon Radioprotection Editorial Board