Simulation and Design Study of Edge-on GaAs:Cr Detector for Clinical Photon Counting CT

Chromium-compensated Gallium Arsenide (GaAs:Cr) has emerged as a promising sensor material for photon counting detectors (PCDs) due to its excellent resistivity and charge carrier mobility. However, due to the limitations of the Cr compensation process, the GaAs:Cr wafer thickness is less than 1 mm, which distorts its X-ray absorption efficiency and limits its application in clinical computed tomography (CT). This study proposes a GaAs detector with an edge-on structure for clinical photon counting CT (PCCT) applications. To evaluate the performance of the detector, we modeled the spectral response and analyzed material decomposition (MD) noise using a full-chain detector model. In imaging domain study, digital phantoms, such as low contrast phantom, Gammex phantom, and XCAT digital phantoms, were virtually scanned to assess the image uniformity, CT number accuracy, material decomposition, and virtual mono-energetic imaging (VMI) performance, with the detector system modeled to reflect actual PCCT prototypes. The results indicate that the GaAs:Cr detector exhibits excellent mono-energetic spectrum response and low material decomposition (MD) noise. Additionally, the GaAs:Cr detector provides lower noise, higher contrast-to-noise ratio (CNR) in VMI results, and more precise concentration measurements in quantitative analysis, compared to existing PCDs. These findings highlight the feasibility of developing GaAs:Cr detectors for clinical CT applications, offering potential advantages over existing PCDs.