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Photon Counting CT

Since its inception in 1971, the dramatic evolution of Computed Tomography (CT) has led to the steady growth of CT’s role in patient care.

Canon Medical has pioneered many of the technological innovations defining the clinical expansion of CT, such as Area Detectors, Ultra-High Resolution, and Deep Learning Reconstruction. In partnership with Redlen Technologies Inc. (Redlen), a Canon group company, the global leader in photon counting detector design and manufacturing, Canon is currently developing a Photon Counting CT (PCCT) with the potential to improve visualization of small structures and enhance tissue characterization.

Our vision is to use Redlen’s state-of-the-art Photon Counting CT technology empowered by Canon Medical’s leading advancements in system, software, and image reconstruction to improve the quality of medical diagnosis for all patients worldwide.

CANON'S PHOTON COUNTING CT

Canon’s PCCT detector is uniquely constructed using Cadmium Zinc Telluride (CZT). The addition of Zinc to Cadmium Telluride increases the detector’s ability to effectively capture photons, for greater dose efficiency. In addition, Canon’s exclusive compact read out circuitry is designed to maximize the active area of the detector to achieve the highest geometric dose efficiency. With an optimized pixel size, fast read out, and sophisticated modelling algorithms, Canon’s CZT detector readily combats challenges such as pulse pileup and charge sharing to yield low noise, high-resolution images.

WHAT IS PHOTON COUNTING CT?

Photon counting CT uses a semiconductor material to directly convert each incident photon into an electric signal, which is then quickly read out by detector circuity to effectively “count” each photon individually. When an incident photon strikes the detector, it creates a charge cloud in the detector material proportional to the energy of incident photon. Based on their measured energy, the counted photons are sorted into energy bins that can be utilized by advanced reconstruction techniques to generate optimal image quality and spectral information.

WHAT IS THE MAIN DIFFERENCE OF PHOTON COUNTING FROM CONVENTIONAL CT?

A PCCT measures each photon and its energy directly, whereas with a conventional Energy Integrating Detector (EID) the incident photons are not directly converted to signal. Rather, the absorbed energy of the photons is first converted to light by a scintillator, then that light is converted to an electrical signal by a photodiode. An EID’s output depends on the combined energy of the incident photons. Higher energy photons generate more light than lower energy photons, and thus contribute more heavily towards the EID’s output electrical signal.

BENEFITS OF CANON’S PCCT: IMAGE QUALITY

The key to achieving the best image quality PCCT can offer is reconstruction. Canon Medical’s long history of advances in reconstruction that have shattered the boundaries of image quality performance have led the way for Canon to optimize PCCT image quality for all patient shapes and sizes.

For more optimal dose efficiency, detectors should have as much active area capturing photons as possible. In conventional EIDs, light in one detector pixel can scatter into a neighboring pixel, a phenomenon called optical crosstalk that reduces spatial resolution. Because of this, EIDs require a reflector of finite thickness between the scintillator pixels to prevent crosstalk. However, the presence of this reflector reduces the active area of the detector and, thus, its dose efficiency, especially for small-sized detector pixels. Because PCCT doesn’t use a scintillator, there is no need for reflective material between detector pixels. This greatly improves the dose efficiency of the detector, allowing for smaller detector pixel sizes without dose penalty.

 

PCCT also overcomes a major disadvantage of EID: electronic noise. An EID’s electronic noise is unavoidably combined with true signal into the detector output. When the number of photons is low, electronic noise becomes dominant, degrading image quality. With PCCT, electronic noise from the detector registers below the threshold of lowest energy bin and is thus discarded. In this way, PCCT effectively eliminates electronic noise, which improves image quality.

BENEFITS OF CANON’S PCCT: SPECTRAL

PCCT enables Spectral Imaging with every scan for routine material decomposition. Canon’s exclusive advances in Spectral reconstruction have given Canon unique insight into minimizing noise and maximizing spectral information from PCCT. Because the thresholds for the energy bins are configurable, PCCT can also allow for imaging that targets specific K-edge energies, from common contrast agents, such as iodine and gadolinium, to novel nanoparticles such as gold.

BENEFITS OF CANON'S PCCT: ULTRA-HIGH RESOLUTION (UHR)

PCCT detectors permit the use of small detector pixels. In standard applications, these pixels can be combined to yield improved spatial resolution relative to conventional CT without noise or dose penalty. For applications where increased spatial resolution adds clinical value, these pixels can be read out individually for Ultra-High Spatial Resolution. Canon launched the Aquilion Precision Ultra-High Resolution (UHR) CT system in 2017 and has now obtained over half a decade of expertise in reconstruction and workflow optimization for UHR as well as achieved advances in tube design, table positioning, and gantry vibration to make the most effective use of UHR-CT. With these advances, Canon is posed to lead the way on UHR PCCT for maximum clinical utility and optimal workflow in a busy clinical environment.

THE ADVANTAGE OF REDLEN, A CANON GROUP COMPANY

Redlen has been developing photon counting detector manufacturing technology for over twenty years and is today a leading global supplier of photon counting imaging detectors. In addition to medical imaging, Redlen CZT technology is currently used globally in security scanning, non-destructive industrial scanning, and aerospace applications.

Redlen’s extensive manufacturing experience has resulted in a fully vertically integrated manufacturing system that spans CZT material growth, wafer processing, sensor fabrication, imaging module design, module assembly, module production testing and finally CZT material recycling, all under one roof. As a result, Canon can realize the stable production of the highly precise photon counting CT detectors. Combined with Canon Medical’s sophisticated CT manufacturing capabilities for gantry, tube, and table, the result is a revolutionary step forward in PCCT.

We're currently accumulating knowledge regarding both the technical and clinical benefits of our photon counting CT system.

Scientific papers

  1. Zhan X, Zhang R, Niu X, Hein I, Budden B, Wu S, Markov N, Clarke C, Qiang Y, Taguchi H, Nomura K, Muramatsu Y, Yu Z, Kobayashi T, Thompson R, Miyazaki H, Nakai H. Comprehensive evaluations of a prototype full field-of-view photon counting CT system through phantom studies. Phys Med Biol. 2023 Aug 14;68(17). doi: 10.1088/1361-6560/acebb3. PMID: 37506710.
  2. Lee D, Zhan X, Tai WY, Zbijewski W, Taguchi K. Improving model-data mismatch for photon-counting detector model using global and local model parameters. Med Phys. 2023 Dec 8. doi: 10.1002/mp.16883. Epub ahead of print. PMID: 38064641.
  3. Sasaki T, Kuno H, Nomura K, Muramatsu Y, Aokage K, Samejima J, Taki T, Goto E, Wakabayashi M, Furuya H, Taguchi H, Kobayashi T.CZT-based photon-counting-detector CT with deep-learning reconstruction: image quality and diagnostic confidence for lung tumor assessment.Jpn J Radiol. 2025 Mar 7. doi: 10.1007/s11604-025-01759-9. Online ahead of print. PMID: 40053285.


Conference presentations

  1. Y. Nakamura et al. Utility of CZT-based photon counting detector CT for a abdominal thin-slice non-contrast CT images in comparison with energy integrating detector CT. ECR 2025
  2. Y. Nakamura et al. Utility of virtual non-contrast images derived from CZT-based photon counting detector CT in comparison with tru non-contrast images. ECR 2025
  3. H. Kuno et al. Imaging-detected Extranodal Extension in Head and Neck Cancer: Clinical Implications and Diagnostic Criteria in the Era of High-Resolution Imaging including Photon-Counting Detector CT. RSNA 2024
  4. T. Sataki et al. CZT-based Photon-Counting-Detector CT with Deep-Learning Reconstruction: Image Quality and Diagnostic Confidence for Lung Tumor Assessment. RSNA 2024
  5. K. Nomura et al. Sharpness Evaluation of Chest Multi Planar Reconstruction Images with Normal and Super High-resolution Mode of CZT-Based Photon-counting Detector CT. RSNA 2024
  6. A. Pourmorteza et al. Dose-Efficient Characterization of Coronary Artery Plaques with a Prototype CdZnTe-Based Photon-Counting CT Scanner. SPIE 2024
  7. A. Pourmorteza et al. Iodine Quantification with a CdZnTe Clinical Prototype Photon-Counting Scanner At Reduced Radiation Dose: Initial Cardiac Phantom Results, ECR 2024
  8. K. Mei et al. Ultra-low-dose photon-counting CT: Assessing radiomic features with a patient-based lung phantom, ECR 2024
  9. S. Mochinaga et al. First Results of Electron Density Quantification with CZT-based Photon Counting Detector CT, ECR 2024
  10. W. Fukumoto et al. Comparison of newly developed CZT-based Photon Counting Detector CT (PCD-CT) and Ultra-High-Resolution CT (U-HRCT) for measuring airway dimensions: A phantom study. ECR 2024
  11. K. Yokomachi et al. Physical characteristics in slice direction using a newly developed CZT-based Photon-Counting Detector CT. ECR 2024
  12. Y. Nakamura et al. Accuracy of CT values on virtual monochromatic images of CZT-based Photon Counting Detector CT: comparison with dual-energy CT using energy integrating detector in a phantom model. ECR 2024
  13. T. Higaki et al. Utility of multi-energy mode of CZT-based Photon Counting Detector CT for coronary CT angiography: A structured phantom study. ECR 2024
  14. D. Lee et al. Advanced Photon-Counting Detector Simulator with a Count-Rate-Dependent Mapping Operator and a Pixel-to-Pixel Variation Generator. IEEE MSS MIC 2023
  15. A. Pourmorteza et al. Dose-efficient Ultra-high-resolution imaging of coronary stents with a CdZnTe-based clinical prototype photon- counting scanner. RSNA 2023
  16. K. L. Boedeker et al. Technical Performance of Super Resolution Deep Learning Reconstruction Algorithm on a Wide Area, Conventional Energy-Integrating Detector vs and a Photon-Counting Computed Tomography System with Conventional Reconstruction Algorithms. RSNA 2023
  17. T. Sasaki et al. CT Imaging of Lung Cancer: Exploring the Clinical Potential of CZT-based Photon Counting Detector CT. RSNA 2023
  18. K. Hirayama et al. Super-high-resolution abdominal imaging using CZT based photon counting CT with deep learning reconstruction: quantitative study and first clinical impression. RSNA 2023
  19. K. Nomura et al. Super-high-resolution chest imaging using CZT-based photon counting CT: performance characterization and first clinical trial. RSNA 2023
  20. S. Mochinaga et al. High z-axis resolution imaging using CZT based photon counting CT: quantitative study and first clinical trial. RSNA 2023
  21. Kei Mei et al. Evaluation of a prototype photon-counting CT for pulmonary imaging using patient-based lung phantoms. RSNA 2023
  22. S. Kondo et al. Visualization of simulated small vessels on photon counting detector CT: comparison with energy integrating CT in a phantom model. RSNA 2023
  23. T. Higaki et al. Improving spatial resolution in coronary CT angiography with photon counting detector CT: A structured phantom study. RSNA 2023
  24. T. Higaki et al. Noise reduction in coronary CT angiography with photon counting detector CT: A structured phantom study. RSNA 2023
  25. F. Tatsugami et al. Coronary Artery Calcium Volume Measurement: A Comparison between Photon-Counting CT and Ultra-High-Resolution CT using a Cardiac CT Calibration Phantom. RSNA 2023
  26. K. Nomura et al. Basic Image Quality Evaluation of New Platform Prototype Photon Counting CT. JRC 2023
  27. X. Zhan,et al. Spectral imaging performance evaluation for a prototype full-size photon counting CT system at clinical dose levels. JRC 2023
  28. R. Zhang,et al. Quantitative image quality comparison between normal resolution and super high resolution modes of a clinical prototype photon counting CT system. JRC 2023
  29. T. W. Holmes et al. Pediatric head and neck imaging with a CZT-based photon-counting CT scanner : initial image quality evaluation. ECR 2023
  30. K. Nomura et al. Comparison of CT image quality for different sized phantom between prototype full-size photon counting and conventional CT systems : CT number, image noise and artifact. ECR 2023
  31. Edgar Salazar et al. Evaluation of a prototype photon-counting CT for low-dose pulmonary imaging using patient-based lung phantom. ECR 2023
  32. X. Zhan et al. A study of cross-talk effect in pixelated photon counting detectors and impact to system imaging performance. SPIE 2023
  33. Donghyeon Lee et al. Photon-Counting Detector Model Using Local Parameters For Pixel-to-Pixel Variation. SPIE 2023
  34. W. Yang Tai et al. Effects of Bowtie Scatter on Material Decomposition in Photon-Counting CT. SPIE 2023
  35. R. Zhang et al. Quantitative Image Quality Comparison between Photon Counting and Conventional CT Systems: Contrast-to-Noise Ratio. RSNA 2022
  36. K. L. Boedeker et al. Low Contrast Detectability Comparison Between a Prototype Photon Counting Computed Tomography System and Conventional CT system Across a Range of Attenuation Levels. RSNA 2022
  37. Xiaohui Z et al. Quantitative image quality evaluation for a prototype photon counting CT through phantom studies: Noise, Resolution and Quantitative Accuracy. CERN SpecXray 2022
  38. A. Pourmorteza et al. First experience with a clinical prototype CZT-based PCCT scanner: applications in low-dose lung cancer screening. CERN SpecXray 2022
  39. Xiaohui Z et al. Phantom imaging evaluations of a prototype CZT based photon counting system. ECR 2022
  40. K. Nomura et al. Quantitative image quality comparison between a prototype full-size photon counting CT system and conventional CT systems with energy integrating detectors. ECR 2022
  41. T. W. Holmes et al. Low-Dose Lung Cancer Screening with a Novel CZT Photon-Counting CT Prototype: A Phantom Study. ECR 2022
  42. Y Suzuki et al. Physics Performance Evaluation of Prototype Photon Counting CT: Basic Image Quality Evaluation. JRC 2022
  43. K. Nomura et al. Physics Performance Evaluation of Prototype Photon Counting CT: Quantitative Evaluation. JRC 2022
  44. Y. Muramatsu et al. Physics Performance Evaluation of Prototype Photon Counting CT: Large-phantom Evaluation. JRC 2022
  45. Xiaohui Z et al. First results from a prototype full-size photon counting CT system: counting and spectral imaging performance at clinical dose levels. RSNA 2021
  46. K. Nomura et al. Quantitative image quality comparison between photon counting and conventional CT systems: noise, resolution and quantitative accuracy. RSNA 2021

Press Releases

August 31, 2021
Commencement of Research Collaboration into Japan's first Photon Counting Computed Tomography with National Cancer Center Japan (medical.canon)

November 7, 2022
First Domestically Produced X-ray CT System with Photon-counting Detector Installed at National Cancer Center Japan Exploratory Oncology Research ＆ Clinical Trial Center (medical.canon)

April 12, 2023
Start of Clinical Research of the First Japanese Produced Next-Generation Photon-Counting Computed Tomography

November 17, 2023
Canon Medical Systems Accelerates Global Clinical Research to Realize Next-Generation Photon-Counting CT

February 26, 2024
Clinical Research on Photon-Counting CT Begins with Radboud University Medical Center

April 8, 2024
Start of Clinical Research with Hiroshima University on Photon-Counting CT

November 27, 2024
Canon Launches Research Collaboration with Penn Medicine for Application of Photon-Counting CT


Disclaimer
Note: Photon Counting CT technology is currently under development and the subject of ongoing research and development. Each technology is not yet commercialized and is not available for sale.