Congress:
EuroSafe Imaging 2020
Keywords:
Action 2 - Clinical diagnostic reference levels (DRLs), Abdomen, Thorax, CT, Diagnostic procedure, Dosimetric comparison, Retrospective, Observational, Multicentre study
Authors:
H. Brat, B. dufour, P. Pujadas, B. Rizk, D. Fournier, F. Zanca
DOI:
10.26044/esi2020/ESI-13030
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.