Optimization of energy thresholds in photon-counting CT via a virtual clinical trial

Ehsan Abadi; Jayasai Rajagopal; Thomas Sauer; Elizabeth Jones; W. Paul Segars; Ehsan Samei

doi:10.1117/12.2549055

Optimization of energy thresholds in photon-counting CT via a virtual clinical trial

Ehsan Abadi, Jayasai Rajagopal, Thomas Sauer, Elizabeth Jones, W. Paul Segars, Ehsan Samei

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

1 Scopus citations

Abstract

In photon-counting CT, detector energy thresholds directly affect image quality attributes such as contrast and noise. The purpose of this study was to identify optimum energy thresholds using a comprehensive virtual clinical trial platform. The virtual trial was done using a computational, anthropomorphic phantom and a photon-counting CT simulator. The phantom (adult male, 50^th percentile body mass index) was chosen from the library of extended cardiac-torso (XCAT) phantoms. A vessel growth algorithm was used to model detailed hepatic arteries within the liver. Five computational lesions were inserted to the liver. The phantom was “imaged” with iodinated contrast at three contrast phases, i.e. arterial, portal venous, and delayed phases. All virtual sinograms were simulated using a validated CT simulator (DukeSim) modeling a prototype photon-counting scanner (CounT, Siemens Healthcare). The simulator included an energy- and threshold-dependent detector model accounting for X-ray and electronic effects and noise. At each contrast phase, the phantom was imaged at 35 detector energy threshold combinations with five lower-energy thresholds (20-40 keV) and seven upper-energy thresholds (50-80 keV). For each scan, two “threshold” images (photons detected beyond a threshold) and one “bin” image (photons detected between the two thresholds) were acquired. Noise magnitude, image contrast, and contrast-to-noise ratio (CNR) were measured in the aorta and the liver lesions. Optimum energy thresholds were identified as those yielding higher CNRs. From the simulations, noise magnitude was found to increase and CNR decrease with the increase in energy thresholds. Keeping the low threshold constant, the noise decreased and CNR increased with the increase in the upper energy threshold. Therefore, our results suggest that a combination of a lower threshold at 20-30 keV and upper threshold at 80 keV maximize the image quality. This study demonstrates an application of a virtual trial platform to quantify and optimize the quality of photon-counting CT.

Original language	English
Title of host publication	Medical Imaging 2020
Subtitle of host publication	Physics of Medical Imaging
Editors	Guang-Hong Chen, Hilde Bosmans
Publisher	SPIE
ISBN (Electronic)	9781510633919
DOIs	https://doi.org/10.1117/12.2549055
State	Published - 2020
Externally published	Yes
Event	Medical Imaging 2020: Physics of Medical Imaging - Houston, United States Duration: Feb 16 2020 → Feb 19 2020

Publication series

Name	Progress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume	11312
ISSN (Print)	1605-7422

Conference

Conference	Medical Imaging 2020: Physics of Medical Imaging
Country/Territory	United States
City	Houston
Period	02/16/20 → 02/19/20

Funding

This study was supported by a research grant from the National Institutes of Health (R01EB001838).

Keywords

CT simulator
Computed Tomography
Photon counting CT
Photon-counting detector
Virtual clinical trial

Access to Document

10.1117/12.2549055

Cite this

Abadi, E., Rajagopal, J., Sauer, T., Jones, E., Segars, W. P., & Samei, E. (2020). Optimization of energy thresholds in photon-counting CT via a virtual clinical trial. In G.-H. Chen, & H. Bosmans (Eds.), Medical Imaging 2020: Physics of Medical Imaging Article 113121Y (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 11312). SPIE. https://doi.org/10.1117/12.2549055

@inproceedings{c700f3d037a648eabcb7b6bc3879275c,

title = "Optimization of energy thresholds in photon-counting CT via a virtual clinical trial",

abstract = "In photon-counting CT, detector energy thresholds directly affect image quality attributes such as contrast and noise. The purpose of this study was to identify optimum energy thresholds using a comprehensive virtual clinical trial platform. The virtual trial was done using a computational, anthropomorphic phantom and a photon-counting CT simulator. The phantom (adult male, 50th percentile body mass index) was chosen from the library of extended cardiac-torso (XCAT) phantoms. A vessel growth algorithm was used to model detailed hepatic arteries within the liver. Five computational lesions were inserted to the liver. The phantom was “imaged” with iodinated contrast at three contrast phases, i.e. arterial, portal venous, and delayed phases. All virtual sinograms were simulated using a validated CT simulator (DukeSim) modeling a prototype photon-counting scanner (CounT, Siemens Healthcare). The simulator included an energy- and threshold-dependent detector model accounting for X-ray and electronic effects and noise. At each contrast phase, the phantom was imaged at 35 detector energy threshold combinations with five lower-energy thresholds (20-40 keV) and seven upper-energy thresholds (50-80 keV). For each scan, two “threshold” images (photons detected beyond a threshold) and one “bin” image (photons detected between the two thresholds) were acquired. Noise magnitude, image contrast, and contrast-to-noise ratio (CNR) were measured in the aorta and the liver lesions. Optimum energy thresholds were identified as those yielding higher CNRs. From the simulations, noise magnitude was found to increase and CNR decrease with the increase in energy thresholds. Keeping the low threshold constant, the noise decreased and CNR increased with the increase in the upper energy threshold. Therefore, our results suggest that a combination of a lower threshold at 20-30 keV and upper threshold at 80 keV maximize the image quality. This study demonstrates an application of a virtual trial platform to quantify and optimize the quality of photon-counting CT.",

keywords = "CT simulator, Computed Tomography, Photon counting CT, Photon-counting detector, Virtual clinical trial",

author = "Ehsan Abadi and Jayasai Rajagopal and Thomas Sauer and Elizabeth Jones and Segars, {W. Paul} and Ehsan Samei",

note = "Publisher Copyright: {\textcopyright} 2020 SPIE.; Medical Imaging 2020: Physics of Medical Imaging ; Conference date: 16-02-2020 Through 19-02-2020",

year = "2020",

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language = "English",

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Abadi, E, Rajagopal, J, Sauer, T, Jones, E, Segars, WP & Samei, E 2020, Optimization of energy thresholds in photon-counting CT via a virtual clinical trial. in G-H Chen & H Bosmans (eds), Medical Imaging 2020: Physics of Medical Imaging., 113121Y, Progress in Biomedical Optics and Imaging - Proceedings of SPIE, vol. 11312, SPIE, Medical Imaging 2020: Physics of Medical Imaging, Houston, United States, 02/16/20. https://doi.org/10.1117/12.2549055

Optimization of energy thresholds in photon-counting CT via a virtual clinical trial. / Abadi, Ehsan; Rajagopal, Jayasai; Sauer, Thomas et al.
Medical Imaging 2020: Physics of Medical Imaging. ed. / Guang-Hong Chen; Hilde Bosmans. SPIE, 2020. 113121Y (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 11312).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

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AB - In photon-counting CT, detector energy thresholds directly affect image quality attributes such as contrast and noise. The purpose of this study was to identify optimum energy thresholds using a comprehensive virtual clinical trial platform. The virtual trial was done using a computational, anthropomorphic phantom and a photon-counting CT simulator. The phantom (adult male, 50th percentile body mass index) was chosen from the library of extended cardiac-torso (XCAT) phantoms. A vessel growth algorithm was used to model detailed hepatic arteries within the liver. Five computational lesions were inserted to the liver. The phantom was “imaged” with iodinated contrast at three contrast phases, i.e. arterial, portal venous, and delayed phases. All virtual sinograms were simulated using a validated CT simulator (DukeSim) modeling a prototype photon-counting scanner (CounT, Siemens Healthcare). The simulator included an energy- and threshold-dependent detector model accounting for X-ray and electronic effects and noise. At each contrast phase, the phantom was imaged at 35 detector energy threshold combinations with five lower-energy thresholds (20-40 keV) and seven upper-energy thresholds (50-80 keV). For each scan, two “threshold” images (photons detected beyond a threshold) and one “bin” image (photons detected between the two thresholds) were acquired. Noise magnitude, image contrast, and contrast-to-noise ratio (CNR) were measured in the aorta and the liver lesions. Optimum energy thresholds were identified as those yielding higher CNRs. From the simulations, noise magnitude was found to increase and CNR decrease with the increase in energy thresholds. Keeping the low threshold constant, the noise decreased and CNR increased with the increase in the upper energy threshold. Therefore, our results suggest that a combination of a lower threshold at 20-30 keV and upper threshold at 80 keV maximize the image quality. This study demonstrates an application of a virtual trial platform to quantify and optimize the quality of photon-counting CT.

KW - CT simulator

KW - Computed Tomography

KW - Photon counting CT

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T3 - Progress in Biomedical Optics and Imaging - Proceedings of SPIE

BT - Medical Imaging 2020

A2 - Chen, Guang-Hong

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T2 - Medical Imaging 2020: Physics of Medical Imaging

Y2 - 16 February 2020 through 19 February 2020

ER -

Optimization of energy thresholds in photon-counting CT via a virtual clinical trial

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