Charge integration-based pulse pileup correction in photon counting detectors

Kevin Treb; Jeff Radtke; Ke Li

doi:10.1117/12.2654235

7 April 2023 Charge integration-based pulse pileup correction in photon counting detectors

Kevin Treb, Jeff Radtke, Ke Li

Proceedings Volume 12463, Medical Imaging 2023: Physics of Medical Imaging; 124633H (2023) https://doi.org/10.1117/12.2654235
Event: SPIE Medical Imaging, 2023, San Diego, California, United States

Abstract

In photon counting detectors (PCDs), electric pulses induced by two or more x-ray photons can pileup when their temporal separation is less than the detector deadtime. Pulse pileups degrade the quantitative accuracy of PCD projection and CT images. In contrast, conventional energy integrating detectors (EIDs) that integrate x-ray induced electric charge are linear with x-ray flux without suffering from pileup losses even at high flux levels. This work presents a novel PCD readout circuit design that leverages the fact that the total induced charge is linearly related to the true input flux to correct for pileup-induced count losses in PCDs. The method only requires an inexpensive upgrade to the existing PCD circuits to record the accumulated charges. After collecting PCD counts and the integrated charges, a lookup table was used to estimate the true photon events. Proof-of-concept experiments were performed with a CdTe-based PCD, and an EID was used to emulate the proposed charge summing component of the readout circuit. With the proposed correction, PCD counts became linear with input flux, even under severe pulse pileup conditions where the PCD is paralyzed and the uncorrected counts start to decrease with increasing flux. Without the correction, post-log sinograms for the test objects were severely overestimated; with the proposed correction, the sinograms accurately represent the true radiological path lengths of the objects. Lastly, no impact on spatial resolution was observed after the proposed correction in images of a spatial resolution test pattern.

Citation Download Citation

Kevin Treb, Jeff Radtke, and Ke Li "Charge integration-based pulse pileup correction in photon counting detectors", Proc. SPIE 12463, Medical Imaging 2023: Physics of Medical Imaging, 124633H (7 April 2023); https://doi.org/10.1117/12.2654235

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KEYWORDS

X-rays

Photon counting

X-ray detectors

Spatial resolution

Capacitors

Analog to digital converters

Design and modelling

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