Local DRLs and automated risk estimation in paediatric interventional cardiology

Introduction Cardiac catheterization procedures result in high radiation doses and often multiple procedures are necessary for congenital heart disease patients. However, diagnostic reference levels (DRL) remain scarce. Our first goal was finding the optimal DRL parameter and determining appropriate DRLs. The second goal was to calculate organ doses (OD), effective doses (ED) and lifetime attributable risks (LAR) per procedure and to provide conversion factors based on dose area product (DAP). Materials and methods DRLs are calculated for each procedure type, as the 75 ^th percentile of the cumulative value per procedure from the corresponding parameter. All irradiation events in the DICOM Structured Reports were automatically processed and simulated using PCXMC, resulting in OD, ED and LAR. Using a Kruskal Wallis H test and subsequent pairwise comparisons, differences in median values of the DRL parameter between procedure types were assessed. Results Linear regression showed a strong correlation and narrow confidence interval between DAP and product of body weight and fluoroscopy time (BWxFT), even when all procedures (diagnostic and interventional) are combined. Only 15% of the pairwise comparisons were statistically significant for DAP normalized to BWxFT (DAP _BWxFT). The latter pairs contained less frequent procedure types with significant outliers. For DAP normalized to BW (DAP _BW), 38% of the pairwise comparisons showed statistically significant differences. Conversion factors from DAP _BW to OD and ED were reported for various weight groups, due to the higher correlation between DAP _BW and both OD and ED than between DAP and both OD and ED. Conclusions The P75 of DAP _BWxFT for all procedures combined serves as an appropriate DRL value. This facilitates local DRL determination in smaller paediatric centres, which often have insufficient data to produce appropriate DRLs for different procedure types. Conversion factors are more reliable starting from DAP _BW instead of DAP and should be used according to the appropriate BW group.