Modeling Photon Counting Detector Anode Street Impact on Detector Energy Response

Accurate modeling of a photon-counting detector is essential for detector design and performance evaluation, system-level performance investigation, and image reconstruction. This modeling is complicated because various factors involve and couple together, including X-ray interactions, fluorescence X-rays escaping and absorption, primary charge cloud distribution, charge diffusion and interactions (repulsion), and charge trapping. In this article, we adapted a comprehensive detector modeling approach, which incorporates all these relevant factors into account. This approach allowed us to evaluate the impact of different physical effects on the detector energy response. In particular, we evaluated the impact of anode street impact on the detector energy response. We found the conductivity difference between the anode street surface and the bulk region within the sensor volume could significantly affect the detector energy response, including reducing peak events and increasing the low-energy tail events. As compared to without considering the anode street conductivity difference, the detection efficiency at 60 keV could be reduced by 5%–15% (40- $\mu \text{m}$ street size), and 12%–33% (70- $\mu \text{m}$ street size) when the threshold was varied from 45 to 57 keV.