Modelling the impact of including the charge carrier creation and transport in photon counting detectors on the radiographic image formation

The study investigates the impact of detailed semiconductor detector modeling on image quality in photon counting detectors, which offer enhanced contrast, intrinsic spectral imaging, and reduced electronic noise. However, common Monte Carlo codes used in radiation detection simulations often simplify important factors, such as sensor bias and crystalline structure. This study aims to simulate chest images using both the original PENELOPE code and the THOR code extension, which models electron-hole pair (EHP) creation and transport. The simulation setup includes a polyenergetic X-ray source (40-80 kV), a newborn anthropomorphic phantom, a carbon fiber table, and a 1 mm thick CdTe detector biased at -300 V. Image quality was assessed using contrast and signal-to-noise ratio (SNR). The THOR code produced images with 50% fewer counts due to EHP losses, particularly from charge trapping, resulting in lower contrast and SNR compared to the PENELOPE code, with relative differences of up to 6.75% and 39%, respectively. This study presents the impact of a detailed modeling of semiconductor detectors and reveals how neglecting this model leads to an overestimation of image quality.