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
Description of activity and work performed
Purpose: The aim of this study was to compare CTDIvol to SSDE as CDRL quantity, in adult chest and abdomen examinations.
Data collection: From February 2017 to June 2018, after protocol optimization according to clinical indication and BMI class (< 25; ≥ 25), 5310 abdomen and 1058 chest CT series were collected from 5 CT scanners in a multicenter group (Table 1).
The 11 most recurrent clinical indications for chest and abdomen examinations represented 70% of all referred indications.
Study population (Fig. 1)
Mean age of the patients was 59.7 years (range 16-101).
53.5% of the patients were female and 46.5% male.
The overweight population (BMI>25) represented 56% of the population.
Method: Local CDRLs based on CTDIvol and on SSDE, stratified per BMI class, were compared.
Results: For chest (Fig. 2) and abdomen (Fig. 3) examinations, the CDRLs based on SSDE were :
- higher than CTDIvol-based CDRLs for small patients (BMI<25)
- comparable for overweight patients (BMI> 25) in all clinical indications
Largest differences were observed in non-overweight patients for pneumonia (4.9 mGy CTDIvol vs 6.3 mGy SSDE, +28.5%) and renal tumor (4.6 mGy CTDIvol vs 8.2 mGy SSDE, +78%), due to a small Deff greatly impacting the CTDIvol conversion factor.
A clear correlation between BMI and Effective diameter was observed (Fig. 4). However, outliers in small Deff population need investigation in order to be able to generalize this correlation.