Dose assessment for chest X-ray examination based on a voxelised human model

Abstract

This study proposes to implement a realistic X-ray source and a high definition voxelised human model, VIP-Man into a Monte Carlo simulation for chest examination. A detailed simulation of a diagnostic X-ray dose requires three major inputs: operation conditions, X-ray spectral and spatial distributions, and a human model. This study collected commonly-used operation parameters such as kVp, mAs, and SSD for chest X-ray examinations. These parameters were inputted to a Monte Carlo code, BEAMnrc, to build a virtual X-ray machine for calculating X-ray spectral and spatial distributions. After that, a high resolution voxelised human model, VIP-Man, was constructed from a segmented Visible Male Dataset, and was irradiated with our virtual X-ray machine. X-ray spectra simulated using BEAMnrc were almost identical to those listed in the literature, or from a spectra simulator, XCOMP3. Heel effects could be observed in our simulation of X-ray spatial distribution. The simulated organ doses were compared to those published in NRPB-R262. There is some significant dose deviation between our results and NRPB’s, owing to the differences in stature and anatomical features, especially for liver, GI tract, lung, pancreas, and red bone marrow. These deviations are mainly caused by the different volume and position of the organs between the mathematical model and VIP-Man.