Long-term experience and analysis of data on diagnostic reference levels: the good, the bad, and the ugly.

OBJECTIVES: To analyze 11-year data of France for temporal trends in dose indices and dose optimization and draw lessons for those who are willing to work on creation and update of diagnostic reference levels (DRLs). METHODS: The data from about 3000 radiology departments leading to about 750,000 imaging exams between 2004 and 2015 was analyzed, and patterns of reductions in dose for those below and above the DRLs were estimated and correlated with technology change. RESULTS: Dose optimization achieved was important and significant in departments which were above or just below the DRL (p = .006) but not in those which were around half of the DRL values. The decrease in 75th percentile value of Kerma air product (KAP) for chest radiography by 27.4% between 2004 and 2015 was observed with the number of flat panel detectors increase from 6 to 43%. A good correlation between the detector type distribution and the level of patient radiation exposure is observed. Otherwise, setting DRLs for standard-sized patient excludes patients lower and higher weighted than "standard." CONCLUSIONS: The concept of DRL may become obsolete unless lessons drawn from the experience of users are taken into account. While establishing DRLs should be part of the regulations, setting up and updating values should be governed by bodies whose decision-making cycle is short, at the most 1 year. A local rather than national approach, taking into account body habitus and image quality, needs to be organized. KEY POINTS: • The technology changes faster than regulations. Requirement of DRL establishment should be part of the regulations; however, setting and updating values should be the role of professional societies. • The concept of DRL, highlighting the 75th percentile values and dedicated to standard-sized adult, misses optimization opportunities in the majority of patients who are below the 75th percentile value and outside the range of standard-sized adult. • The ugly aspects of the DRL concept include its non-applicability to individuals, no customization to clinical indications, and lack of consideration of image quality.

Using diagnostic reference levels to evaluate the improvement of patient dose optimisation and the influence of recent technologies in radiography and computed tomography.

OBJECTIVES: Twelve years since the implementation of Diagnostic Reference Levels (DRL) process in France, the Nuclear Safety and Radiation Protection French Institute (IRSN) presents its latest analyses performed on the most recent national data. METHODS: Statutorily, each year, medical imaging departments must perform patient exposure evaluation from their clinical practice for at least 2 types of radiographic and computed tomography (CT) examinations freely chosen in the regulatory list. The samples of dosimetric data used for the evaluations must be sent to IRSN for national assessment using a dedicated and secured web portal. The analyses of collected data for radiography and CT allow IRSN to estimate the representativeness of current DRLs in terms of target practices and examinations, dosimetric quantities and numerical values. Technical data are transmitted, such as detector type in radiography or commissioning date of CT, and are included in some complementary analyses in order to evaluate their influence on patient exposure. RESULTS: Since 2004 the involvement of professionals in the DRL process has highly increased in CT (about 80% in 2015) but remains quite weak in radiography (almost 30%). Analyses show some discordance between regulation references and clinical practice leading to clinical doses data which are 40% lower than DRLs in 2015. As a consequence, the list of examinations types and some numerical values should be updated in the regulation. Focused analyses show a significant patient exposure reduction when digital radiography is used and when CT equipment is under five years old. CONCLUSIONS: Based on these findings, IRSN recommends to update DRL regulation with current and relevant examination lists, dosimetric quantities and numerical values. In addition, this study shows that technology and generation of equipment, such as detector type in radiography or image reconstruction algorithm in CT, take an important place in the dose optimisation process, enabling significant patient exposure reduction when it is associated with protocols optimisation.

PATIENT EXPOSURE FROM NUCLEAR MEDICINE IN FRANCE: NATIONAL FOLLOW-UP AND INFLUENCE OF THE TECHNOLOGY THROUGH DIAGNOSTIC REFERENCE LEVELS DATA ANALYSIS.

The Nuclear Safety and Radiation Protection French Institute (IRSN) presents its latest assessment from up-to-date diagnostic reference levels (DRL) national data in nuclear medicine (NM). NM departments annually send data to IRSN to estimate the representativeness of current DRLs. Complementary analyses of the data have been performed to evaluate the influence of equipment evolution on practice and patient radiation exposure. Based on data from almost 90% of the French NM departments, some DRL update are proposed. The analysis of positron emission tomography data show that the more the time of flight technology is available on equipment, the lower is the administered activity to the patient. IRSN recommends updating DRL regulation with current and relevant examination data. The influence of technology evolution appeared to be positive for patient exposure and the results showed an obvious involvement of professionals in the radiation dose optimisation process.