Simulations of X-ray spectra, half value layer, and mean energy from mammography using EGSnrc Monte Carlo and SpekPy

This study presents the simulation results of X-ray spectra, half value layers (HVLs), and mean energies (E_mean) of two mammography units using EGSnrc Monte Carlo (MC) and SpekPy computer codes.

The spectra caused by different combinations of targets/filters at various tube voltages (kVps) of two mammography units were simulated using two different computer codes. The EGSnrc MC simulated data of spectra and E_mean were compared with those obtained from SpekPy. The simulated values of two units' HVLs obtained from two computer codes were compared with those from physical measurements from mammography machines used in clinical practice.

The maximum discrepancies in E_mean simulated from two codes were less than 4.1% and 1.5% for the target/filter combination of W/Rh and Mo/Mo, respectively. The HVLs of the SpekPy were well matched to the physical measurements. The percentage differences were within 3.3% and 6.8% for two units, respectively. The EGSnrc MC simulated values of HVLs show the percentage differences within 8.9% and 7.0% with those from physical measurements for two units, respectively. All methods of HVLs determination comply with the requirements of IAEA Human Health Series No.17.

The HVLs, E_mean, spectra varied depending on the target/filter combinations and composition of the mammography tubes. The simulation results verify that the HVLs evaluation using the EGSnrc MC and SpekPy can be validated for mammography standard beam qualities and provide prediction almost immediately compared with physical experiments.

EGSnrc MC and SpekPy have been considered powerful toolkits to simulate typical X-ray tubes used in mammography due to the good agreement between the calculation of E_mean, physical measurements and simulated HVLs.