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The technical development of photon-counting detector CT

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Abstract

Since 1971 and Hounsfield’s first CT system, clinical CT systems have used scintillating energy-integrating detectors (EIDs) that use a two-step detection process. First, the X-ray energy is converted into visible light, and second, the visible light is converted to electronic signals. An alternative, one-step, direct X-ray conversion process using energy-resolving, photon-counting detectors (PCDs) has been studied in detail and early clinical benefits reported using investigational PCD-CT systems. Subsequently, the first clinical PCD-CT system was commercially introduced in 2021. Relative to EIDs, PCDs offer better spatial resolution, higher contrast-to-noise ratio, elimination of electronic noise, improved dose efficiency, and routine multi-energy imaging. In this review article, we provide a technical introduction to the use of PCDs for CT imaging and describe their benefits, limitations, and potential technical improvements. We discuss different implementations of PCD-CT ranging from small-animal systems to whole-body clinical scanners and summarize the imaging benefits of PCDs reported using preclinical and clinical systems.

Key Points

• Energy-resolving, photon-counting-detector CT is an important advance in CT technology.

• Relative to current energy-integrating scintillating detectors, energy-resolving, photon-counting-detector CT offers improved spatial resolution, improved contrast-to-noise ratio, elimination of electronic noise, increased radiation and iodine dose efficiency, and simultaneous multi-energy imaging.

• High-spatial-resolution, multi-energy imaging using energy-resolving, photon-counting-detector CT has been used in investigations into new imaging approaches, including multi-contrast imaging.

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Abbreviations

ASIC:

Application-specific integrated circuits

CdTe:

Cadmium telluride

CZT:

Cadmium zinc telluride

EID:

Energy-integrating detector

FOV:

Field of view

PCD:

Photon-counting detector

UHR:

Ultra-high resolution

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Acknowledgements

Portions of the work presented were supported by the National Institutes of Health under award number R01 EB028590. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. In-kind support was received from Siemens Healthineers, who owns the system uses for image acquisition under the terms of a sponsored research agreement with Mayo Clinic. The authors thank Mr. Kevin Kimlinger for his assistance with manuscript preparation.

Funding

This study has received funding by the NIH and Siemens Healthineers.

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Authors and Affiliations

  1. Department of Radiology, Mayo Clinic, Rochester, MN, USA

    Cynthia H. McCollough, Kishore Rajendran, Shuai Leng, Lifeng Yu & Joel G. Fletcher

  2. Siemens Healthineers, Forchheim, Germany

    Karl Stierstorfer & Thomas G. Flohr

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  1. Cynthia H. McCollough
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Correspondence to Cynthia H. McCollough.

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The scientific guarantor of this publication is Cynthia H. McCollough, PhD.

Conflict of interest

Some authors of this manuscript declare relationships with the following companies:

• Karl Stierstorffer, PhD and Thomas Flohr, PhD are employees of Siemens Healthineers.

• Cynthia McCollough, PhD is the PI of a research grant to Mayo Clinic from Siemens Healthineers.

• Joel G. Fletcher, MD receives research support from a grant to Mayo Clinic from Siemens Healthineers.

Kishore Rajendran, PhD, is a member of the Scientific Editorial Board of European Radiology but has not taken part in the review or selection process of this article.

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McCollough, C.H., Rajendran, K., Leng, S. et al. The technical development of photon-counting detector CT. Eur Radiol 33, 5321–5330 (2023). https://doi.org/10.1007/s00330-023-09545-9

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