A study of crosstalk effect in pixelated photon counting detectors and impact to system imaging performance

Xiaohui Zhan; Shuoxing Wu; Ilmar Hein; Nikolay Markov; Ruoqiao Zhang; Brent Budden; Cameron Clarke; Yi Qiang; Zhou Yu; Richard Thompson; Hiroaki Miyazaki; Hiroaki Nakai

doi:10.1117/12.2654374

7 April 2023 A study of crosstalk effect in pixelated photon counting detectors and impact to system imaging performance

Xiaohui Zhan, Shuoxing Wu, Ilmar Hein, Nikolay Markov, Ruoqiao Zhang, Brent Budden, Cameron Clarke, Yi Qiang, Zhou Yu, Richard Thompson, Hiroaki Miyazaki, Hiroaki Nakai

Author Affiliations +

Proceedings Volume 12463, Medical Imaging 2023: Physics of Medical Imaging; 124630C (2023) https://doi.org/10.1117/12.2654374
Event: SPIE Medical Imaging, 2023, San Diego, California, United States

Abstract

Semiconductor-based photon counting detectors (PCDs) measure each incident photon energy through direct conversion process. Comparing to the conventional scintillator-based energy-integrating detectors (EIDs), it can be made with smaller pixel sizes and hence improve the system spatial resolution. The actual performance of the PCDs in CT system is compromised from ideal mainly due to two factors: charge sharing effect and pulse pileup. In particular, the charge sharing effect introduces signal crosstalk between neighboring pixels and degrade the detection spatial resolution. In this study, we derive a rigorous charge sharing detection formalism based on a comprehensive detector response model. The simulated results are compared with a pixel-to-pixel covariance measurement from a CZT-based prototype photon counting system. The results suggests that while a large fraction of detected events is affected by charge sharing, the actual measured crosstalk between neighboring pixels is greatly suppressed by a proper detection threshold in the counting mode. To understand the practical impact in image quality and optimize system design, a simplified crosstalk model based on the estimated charge sharing event rate is integrated into a system level simulation framework with realistic system specifications. The simulated image MTFs are measured for systems with four different pixel sizes. Results indicate that with realistic charge sharing effect, in the pixel size range that we tested, the image MTF steadily increases as the detector pixel size decreases.

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Xiaohui Zhan, Shuoxing Wu, Ilmar Hein, Nikolay Markov, Ruoqiao Zhang, Brent Budden, Cameron Clarke, Yi Qiang, Zhou Yu, Richard Thompson, Hiroaki Miyazaki, and Hiroaki Nakai "A study of crosstalk effect in pixelated photon counting detectors and impact to system imaging performance", Proc. SPIE 12463, Medical Imaging 2023: Physics of Medical Imaging, 124630C (7 April 2023); https://doi.org/10.1117/12.2654374

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