Photon Counting

The future is Spectral Photon Counting

Photon counting represents the next generation of CT hardware technology. It is an area of significant research both in academia and in the industry that promises to deliver improvements in ultra high resolution, enhanced dose efficiency, and Spectral always on. While systems are currently available for research and patient use, there are still limitations to full routine clinical adoption. At the same time, with its quantitative and analytical imaging technology photon counting is the future of CT.

    The promises of Spectral Photon Counting Technology

    Photon counting technology high image quality

    Ultra High Resolution enabled by significant improvement in resolution. Commercially available systems enable spatial resolution of up to 40 lp/cm. 1

    Photon counting dose efficiency

    Enhanced Dose efficiency by enabling the possibility to use less dose and get more information from each photon. Commercially available systems allow for dose reduction of 32% compared to dual-source CT. 2

    Photon counting technology with additional information

    Spectral always on through detector-based multi-energy acquisition and analysis capabilities.

    Photon Counting Detectors

    Detection principle of photon counting detectors video thumb

    Christoph Herrmann, Philips Research, “Detection principle of Photon Counting Detectors”4

    Unlike the integrated detectors used in conventional scanners, Spectral Photon Counting Detectors are made of CZT (Cadmium Zinc Telluride) semiconductors. The first layer of semiconductor of thickness from 2 to 3mm, allows, by absorbing a photon, to form electron-hole pairs. These detectors are connected to an electronic system (ASIC) composed of parallel channels allowing successively to model the signal and to amplify it so that it is sorted by energy level. The photons are then discriminated in 2 to 8 energy levels chosen beforehand. Operation of the detectors is summarized in the video.3

    The importance of photon counting technology

    In contrast to CT, spectral photon counting systems (SPCCT) doesn’t just capture the volume of photons that make it through – it also measures the energy of each photon. As a result, much like we perceive different photon energy levels as different colors of light, SPCCT enables clinicians to ‘see’ X-rays in full color.5

    • Multi-Energy CT images can be acquired with different technologies and scan modes
    • Source-based techniques require two data sets while detection-based techniques achieve it in one scan
    • Advanced use case: It will be possible to see separation of different materials allowing for targeted contrast agents

    Challenges with current designs

    Radiologist in discussion

    Philips pioneers research into next generation of CT imaging

    SPCCT system

    As part of an EU-funded consortium, Philips is pioneering research into the next generation of CT imaging: Spectral Photon Counting CT (SPCCT).

    Philips’ clinical prototype is the world’s first full-field-of-view SPCCT system, and has recently been installed at Lyon University Hospital, France.7

    Photon Counting is a work in progress, not FDA cleared.

    Picture of Philippe Douek
    Spectral Photon Counting CT is a new imaging modality based on the usual CT concept with the key difference of energy resolving detector technology. The additional spectral information can be used for material separation and can deliver additional, new contrast with clinically relevant new information.

    Pr Philippe Douek, MD, PhD

    Professor at Hospices Civils de Lyon

    More from the world of Spectral Detector CT

    Discover the next generation of multi-energy CT

    Advantages of a spectral detector-based CT system

    The future of photon counting imaging

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