EuroSafe Imaging 2020
Action 2 - Clinical diagnostic reference levels (DRLs), Abdomen, Thorax, CT, Diagnostic procedure, Dosimetric comparison, Retrospective, Observational, Multicentre study
H. Brat, B. dufour, P. Pujadas, B. Rizk, D. Fournier, F. Zanca
Dose Reference Levels (DRLs) are used in Medical Imaging clinical routine to indicate whether the dose to the patient is unusually high or low for a specific procedure and they are typically defined for anatomical regions.
The typical DRL quantity is volume CT dose index (CTDIvol), which is a standardized dose measurement in homogeneous phantoms and does not account for patient size.
Recently, the International Commission on Radiological Protection (ICRP) publication 135 (1) stressed the importance of clinical DRLs (CDRLs) to define more specific dose levels according to the needed image quality for a specific clinical indication.
- Example: the same DRLs for CT of the chest is applied to a work-up for pulmonary embolism, lung cancer or even coronary calcium scoring, which require different image quality levels, and should have different DRLs, in line with the ALARA principle.
Based on that, the Eurosafe Imaging (European Society of Radiology) has performed a European prospective study (EUCLID, 2018-2019) to develop a set of CDRLs based on clinical indication, to limit large variations in dose levels for the same type of examinations across Europe.
In a recent study by Brat et al. (2), this concept has been extended further and CDRLs based on CTDIvol accounting for patient size through Body-Mass Index (BMI) have been proposed, allowing improved optimization of CT doses.
While these results are very promising and state-of-the art, using a DRL metric which incorporates patient size would be desirable.
In the past years, the concept of Size-Specific Dose Estimates (SSDE) was introduced by the American Association of Physicists in Medicine (AAPM) as a new index of radiation dose (3). It is derived from CTDIvol, by incorporating CTDIvol correction factors in function of patient effective diameter (Deff).
However, it is not always nor easily available before examinations, and has not yet been fully studied as a diagnostic reference level quantity to possibly replace CTDIvol.