Development and validation of XrayMC: a dedicated Monte Carlo tool for X-ray imaging and radiation protection

OBJECTIVE: This work introduces and validates XrayMC, a novel Monte Carlo (MC) simulation tool specifically designed for photon transport and dose scoring in diagnostic X-ray imaging and image-guided interventional procedures. The tool aims to provide accurate, efficient, and flexible simulations for patient and staff dosimetry in complex imaging environments.
Approach: XrayMC implements history-by-history photon transport for energies between 1-150 keV. It supports multiple geometry types such as voxel-grids, triangulated surfaces, and tetrahedral meshes, enabling detailed modelling of patients, staff, and imaging equipment. Common X-ray beam configurations used in diagnostic imaging, such as computed tomography (CT), cone beam CT (CBCT) and planar imaging, are included to make it easier to create clinically relevant X-ray beams. XrayMC is benchmarked against the AAPM Task Group 195 Monte Carlo reference dataset (TG195), with a total of 694 comparisons to reference data across five diagnostic imaging cases, including radiography, mammography, and CT.
Main results: All imaging cases relevant to photon transport in TG195 were successfully replicated in XrayMC, and the results from XrayMC are in excellent agreement with those obtained with the TG195 reference MC packages (EGSnrc, Geant4, MCNP, and Penelope). Across all cases, the average deviation from TG195 was less than 0.5%, and 690 of the 694 comparisons between XrayMC and TG195 differed by less than 2%. The largest difference from the TG195 values was 3.6% for energy scored in the adrenals for CT exposures of a voxel phantom.
Significance: XrayMC provides a tailored and optimised alternative to general-purpose MC codes for imaging applications. Its flexibility in geometry handling and validated accuracy make it suitable for research and clinical dose assessment, supporting improved radiation protection for patients and healthcare professionals. In addition, XrayMC allows visualisation of dose distributions and simulation set-ups that can aid teaching and understanding of radiation protection in imaging applications.