CC BY 4.0 · Journal of Health and Allied Sciences NU 2023; 13(02): 147-152
DOI: 10.1055/s-0042-1749180
Review Article

Photon-Counting Detectors in Computed Tomography: A Review

Muriel Jeremia Gomes
1   Department of Radiodiagnosis and Imaging, Medical Imaging Technology, KS Hegde Medical Academy, Mangalore, Karnataka, India
1   Department of Radiodiagnosis and Imaging, Medical Imaging Technology, KS Hegde Medical Academy, Mangalore, Karnataka, India
› Author Affiliations


Photon-counting computed tomography (CT) is a new technique that has the potential to revolutionize clinical CT and is predicted to be the next significant advancement. In recent years, tremendous research has been conducted to demonstrate the developments in hardware assembly and its working principles. The articles in this review were obtained by conducting a search of the MEDLINE database. Photon-counting detectors (PCDs) provide excellent quality diagnostic images with high spatial resolution, reduced noise, artifacts, increased contrast-to-noise ratio, and multienergy data acquisition as compared with conventionally used energy-integrating detector (EID). The search covered articles published between 2011 and 2021. The title and abstract of each article were reviewed as determined by the search strategy. From these, eligible studies and articles that provided the working and clinical application of PCDs were selected. This article aims to provide a systematic review of the basic working principles of PCDs, emphasize the uses and clinical applications of PCDs, and compare it to EIDs. It provides a nonmathematical explanation and understanding of photon-counting CT systems for radiologists as well as clinicians.


This article reports the current status, basic working principles, and applications of photon-counting detectors (PCD) compared with the conventional EID used for CT scanners.

Publication History

Article published online:
04 July 2022

© 2022. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (

Thieme Medical and Scientific Publishers Pvt. Ltd.
A-12, 2nd Floor, Sector 2, Noida-201301 UP, India

  • References

  • 1 Flohr TCT. Systems. Curr Radiol Rep 2013; 1 (01) 52-63
  • 2 Pelc NJ. Recent and future directions in CT imaging. Ann Biomed Eng 2014; 42 (02) 260-268
  • 3 Hu H, He HD, Foley WD, Fox SH. Four multidetector-row helical CT: image quality and volume coverage speed. Radiology 2000; 215 (01) 55-62
  • 4 Leng S, Bruesewitz M, Tao S. et al. Photon-counting detector CT: system design and clinical applications of an emerging technology. Radiographics 2019; 39 (03) 729-743
  • 5 Swank RK. Absorption and noise in x-ray phosphors. J Appl Phys 1973; 44 (09) 4199-4203
  • 6 Zhou W, Lane JI, Carlson ML. et al. Comparison of a photon-counting-detector CT with an energy-integrating-detector CT for temporal bone imaging: a cadaveric study. AJNR Am J Neuroradiol 2018; 39 (09) 1733-1738
  • 7 Shikhaliev PM, Xu T, Molloi S. Photon counting computed tomography: concept and initial results. Med Phys 2005; 32 (02) 427-436
  • 8 Taguchi K, Iwanczyk JS. Vision 20/20: single photon counting x-ray detectors in medical imaging. Med Phys 2013; 40 (10) 100901 DOI: 10.1118/1.4820371.
  • 9 Leng S, Rajendran K, Gong H. et al. 150-μm spatial resolution using photon-counting detector computed tomography technology: technical performance and first patient images. Invest Radiol 2018; 53 (11) 655-662
  • 10 Symons R, Cork TE, Sahbaee P. et al. Low-dose lung cancer screening with photon-counting CT: a feasibility study. Phys Med Biol 2017; 62 (01) 202-213
  • 11 Flohr T, Ulzheimer S, Petersilka M, Schmidt B. Basic principles and clinical potential of photon-counting detector CT. Chinese J Acad Radiol 2020; 3 (01) 19-34
  • 12 Flohr T, Petersilka M, Henning A, Ulzheimer S, Ferda J, Schmidt B. Photon-counting CT review. Phys Med 2020; 79: 126-136
  • 13 Santarelli MF, Giovannetti G, Hartwig V, Celi S, Positano V, Landini L. The core of medical imaging: state of the art and perspectives on the detectors. Electronics (Basel) 2021; 10 (14) 1642 DOI: 10.3390/electronics10141642.
  • 14 Ferda J, Vendiš T, Flohr T. et al. Computed tomography with a full FOV photon-counting detector in a clinical setting, the first experience. Eur J Radiol 2021; 137: 109614 DOI: 10.1016/j.ejrad.2021.109614.
  • 15 Yu Z, Leng S, Kappler S. et al. Noise performance of low-dose CT: comparison between an energy integrating detector and a photon counting detector using a whole-body research photon counting CT scanner. J Med Imaging (Bellingham) 2016; 3 (04) 043503 DOI: 10.1117/1.JMI.3.4.043503.
  • 16 McCollough CH, Leng S, Yu L, Fletcher JG. Dual- and multi-energy CT: principles, technical approaches, and clinical applications. Radiology 2015; 276 (03) 637-653
  • 17 Goo HW, Goo JM, Dual-Energy CT. Dual-energy CT: new horizon in medical imaging. Korean J Radiol 2017; 18 (04) 555-569
  • 18 Faby S, Kuchenbecker S, Sawall S. et al. Performance of today's dual energy CT and future multi energy CT in virtual non-contrast imaging and in iodine quantification: a simulation study. Med Phys 2015; 42 (07) 4349-4366
  • 19 Iwanczyk JS, Nygård E, Meirav O. et al. Photon counting energy dispersive detector arrays for X-ray imaging. IEEE Trans Nucl Sci 2009; 56 (03) 535-542
  • 20 Schlomka JP, Roessl E, Dorscheid R. et al. Experimental feasibility of multi-energy photon-counting K-edge imaging in pre-clinical computed tomography. Phys Med Biol 2008; 53 (15) 4031-4047
  • 21 Willemink MJ, Persson M, Pourmorteza A, Pelc NJ, Fleischmann D. Photon-counting CT: technical principles and clinical prospects. Radiology 2018; 289 (02) 293-312
  • 22 Leng S, Yu Z, Halaweish A. et al. Dose-efficient ultrahigh-resolution scan mode using a photon counting detector computed tomography system. J Med Imaging (Bellingham) 2016; 3 (04) 043504 DOI: 10.1117/1.JMI.3.4.043504.
  • 23 da Silva J, Grönberg F, Cederström B. et al. Resolution characterization of a silicon-based, photon-counting computed tomography prototype capable of patient scanning. J Med Imaging (Bellingham) 2019; 6 (04) 043502 DOI: 10.1117/1.JMI.6.4.043502.
  • 24 McCollough CH, Leng S, Sunnegardh J. et al. Spatial resolution improvement and dose reduction potential for inner ear CT imaging using a z-axis deconvolution technique. Med Phys 2013; 40 (6, 6Part1): 061904 DOI: 10.1118/1.4802730.
  • 25 W. Richard Webb Nestor L. Müller David P. Naidich. High-Resolution CT of the Lung. fifth edition. (Jonathan W. Pine J, ed.). Wolters Kluwer; 2014
  • 26 Danielsson M, Persson M, Sjölin M. Photon-counting x-ray detectors for CT. Phys Med Biol 2021; 66 (03) 03TR01 DOI: 10.1088/1361-6560/abc5a5.
  • 27 Shikhaliev PM. Beam hardening artefacts in computed tomography with photon counting, charge integrating and energy weighting detectors: a simulation study. Phys Med Biol 2005; 50 (24) 5813-5827
  • 28 Johnson TRC, Dual-Energy CT. Dual-energy CT: general principles. AJR Am J Roentgenol 2012; 199 (5, Suppl): S3-S8
  • 29 Curry TS, Dowdey JE, Murry RC, Christensen EE. Christensen's Physics of Diagnostic Radiology. Philadelphia: Lippincott Williams & Wilkins;; 1998
  • 30 Pérez-Lara A, Forghani R. Spectral computed tomography: technique and applications for head and neck cancer. Magn Reson Imaging Clin N Am 2018; 26 (01) 1-17
  • 31 Coursey CA, Nelson RC, Boll DT. et al. Dual-energy multidetector CT: how does it work, what can it tell us, and when can we use it in abdominopelvic imaging?. Radiographics 2010; 30 (04) 1037-1055
  • 32 Roessl E, Proksa R. K-edge imaging in x-ray computed tomography using multi-bin photon counting detectors. Phys Med Biol 2007; 52 (15) 4679-4696
  • 33 Wang X, Meier D, Taguchi K, Wagenaar DJ, Patt BE, Frey EC. Material separation in x-ray CT with energy resolved photon-counting detectors. Med Phys 2011; 38 (03) 1534-1546
  • 34 Yu Z, Leng S, Jorgensen SM. et al. Evaluation of conventional imaging performance in a research whole-body CT system with a photon-counting detector array. Phys Med Biol 2016; 61 (04) 1572-1595
  • 35 Kidwell CS, Chalela JA, Saver JL. et al. Comparison of MRI and CT for detection of acute intracerebral hemorrhage. JAMA 2004; 292 (15) 1823-1830
  • 36 Kim DS, Na DG, Kim KH. et al. Distinguishing tumefactive demyelinating lesions from glioma or central nervous system lymphoma: added value of unenhanced CT compared with conventional contrast-enhanced MR imaging. Radiology 2009; 251 (02) 467-475
  • 37 Fink KR, Fink JR. Imaging of brain metastases. Surg Neurol Int 2013; 4 (05, Suppl 4): S209-S219
  • 38 Ferrero A, Gutjahr R, Halaweish AF, Leng S, McCollough CH. Characterization of urinary stone composition by use of whole-body, photon-counting detector CT. Acad Radiol 2018; 25 (10) 1270-1276
  • 39 Gutjahr R, Polster C, Henning A. et al. Dual energy CT kidney stone differentiation in photon counting computed tomography. In: Flohr TG, Lo JY, Gilat Schmidt T, eds. 2017; 1013237 DOI: 10.1117/12.2252021
  • 40 Symons R, Krauss B, Sahbaee P. et al. Photon-counting CT for simultaneous imaging of multiple contrast agents in the abdomen: An in vivo study. Med Phys 2017; 44 (10) 5120-5127
  • 41 Ji X, Zhang R, Chen G-H, Li K. Task-driven optimization of the non-spectral mode of photon counting CT for intracranial hemorrhage assessment. Phys Med Biol 2019; 64 (21) 215014 DOI: 10.1088/1361-6560/ab43a6.
  • 42 Mannil M, Hickethier T, von Spiczak J. et al. Photon-Counting CT. Invest Radiol 2018; 53 (03) 143-149
  • 43 Pourmorteza A, Symons R, Henning A, Ulzheimer S, Bluemke DA. Dose efficiency of quarter-millimeter photon-counting computed tomography: first-in-human results. Invest Radiol 2018; 53 (06) 365-372
  • 44 Bartlett DJ, Koo CW, Bartholmai BJ. et al. High-resolution chest computed tomography imaging of the lungs: impact of 1024 matrix reconstruction and photon-counting detector computed tomography. Invest Radiol 2019; 54 (03) 129-137
  • 45 Wetzl M, Wenkel E, Balbach E. et al. Detection of microcalcifications in spiral breast computed tomography with photon-counting detector is feasible: a specimen study. Diagnostics (Basel) 2021; 11 (05) 848 DOI: 10.3390/diagnostics11050848.