Estimation of organ and effective doses in High-Resolution Cone-Beam Computed Tomography (HR-CBCT) during cerebral angiography.

High-resolution cone-beam computed tomography (HR-CBCT) during cerebral angiography raises concerns regarding high radiation exposure in exchange for high spatial resolution, but detailed dose assessments are lacking. This study aimed to accurately estimate organ dose (OD) and effective dose (ED) for HR-CBCT using the NCIRF Monte Carlo software, which incorporates projection-specific variations in X-ray output, and to derive dose conversion coefficients for clinical application. Four sites prone to cerebral aneurysms were scanned using a phantom, and exposure parameters were recorded for each projection angle. OD and ED were calculated using NCIRF. Simulation accuracy was validated by comparing lens doses measured with radiophotoluminescence glass dosimeters, and the results were compared with a conventional method that ignores projection-specific dose variations. The maximum brain OD was 46.2 mGy for males and 61.7 mGy for females. ED ranged from 0.70 to 0.89 mSv for males and 0.86-1.11 mSv for females. The relative difference between simulated and measured lens doses was less than 6.0%, demonstrating good agreement. The proposed method reduced lens dose error by approximately 20% compared to the conventional method. Conversion coefficients were calculated for each site and sex to estimate OD and ED from the air kerma-area product. This study demonstrated that dynamic Monte Carlo simulation incorporating projection-specific exposure variations can provide highly accurate dose estimations for HR-CBCT. The derived conversion coefficients offer a practical tool that can support optimization of patient radiation protection in clinical settings using similar equipment and protocols.