Quantifying Photon Counting Detector (Pcd) Performance Using Pcd-Ct Images

Authors

Linying Zhan
Guang-Hong Chen
Ke Li

Publication Date

5-1-2025

Journal

Medical Physics

DOI

10.1002/mp.17701

PMID

39971720

PMCID

PMC12064383

PubMedCentral® Posted Date

2-19-2025

PubMedCentral® Full Text Version

Post-print

Abstract

Background: Photon counting detector CTs (PCD-CTs) have recently been introduced to clinical imaging. This development creates a new need for end-users to quantify and monitor the physical performance of PCDs. Traditionally, the characterization of PCD performance relied on detector counts, which are typically accessible to the manufacturer but are not usually available to clinical end-users.

Purpose: The goal of this work was to develop a new method for quantifying PCD performance using reconstructed PCD-CT images, without requiring access to the PCD counts.

Methods: The proposed method is based on a set of closed-form relationships that connect PCD-CT image noise, the PCD deadtime ( τ ), and the zero-frequency detective quantum efficiency ( DQE0 ) of PCDs. At a low tube current (mA) level, the mean output counts of the PCD were estimated by fitting the measured PCD-CT noise power spectrum (NPS) to a parametric model. DQE0 was then calculated by normalizing the estimated mean detector counts to the expected input x-ray photon number. To estimate τ , the image variance of PCD-CT was measured at different mA levels. A novel quantitative relationship between PCD-CT image variance, τ , and mA was employed to estimate τ through parametric fitting. The method was validated using both simulated and experimental PCD-CT data, covering a range of τ , DQE0 , and system geometries.

Results: For the simulated curved-detector PCD-CT, the estimation errors for DQE0 and deadtime were -3.7% and 0.5%, respectively. For the simulated collinear-detector PCD-CT, the estimation errors for DQE0 and deadtime were -3.3% and -1.0%, respectively. For the experimental collinear-detector PCD-CT, the estimation errors for DQE0 and deadtime were -2.6% and 1.6%, respectively.

Conclusions: By analyzing the variance and NPS of PCD-CT images, DQE0 and deadtime of scanner's PCD can be accurately estimated, without access to raw detector counts or projection data.

Keywords

Photons, Tomography, X-Ray Computed, Image Processing, Computer-Assisted, Phantoms, Imaging, CT image quality, photon counting detector, photon counting detector CT

Published Open-Access

yes

Recommended Citation

Linying Zhan, Guang-Hong Chen, and Ke Li, "Quantifying Photon Counting Detector (Pcd) Performance Using Pcd-Ct Images" (2025). Faculty, Staff and Student Publications. 4709.
https://digitalcommons.library.tmc.edu/uthgsbs_docs/4709