Photon-counting computed tomography

Dr Yair Glick and Dr Balint Botz et al.

Photon-counting computed tomography (PCCT) is an emerging technology in CT imaging, which could represent the next major technological milestone in the field. Briefly, PCCT uses energy-resolving detectors, thereby enabling scanning at multiple energies.


Current clinical CT systems rely on energy-integrating detectors (EID), which measure the total x-ray energy reaching the detector during the measurement period.  The photon-counting detectors (PCD) in a PCCT system count the exact number of incoming x-ray photons, and also measure their energy individually. As a consequence PCDs always obtain spectral information, and can effectively filter out electronic noise unlike EIDs, resulting in significantly improved signal-to-noise ratio 1-2

Practical points

PCCT readily differentiates between tissue types and contrast agents much like spectral CT. In the future PCCT could offer higher signal-to-noise ratio, better spatial resolution, superior virtual noncontrast imaging, and spectral imaging data much like dual-energy CT currently does. It could reduce radiation exposure, reduce the amount of contrast agent needed, and lower the amount of CT artifacts. It could also make simultaneous imaging with multiple contrast agents (e.g. iodine, gadolinium, or gold nanoparticles) feasible. Unlike conventional CT, PCCT can readily measure the exact concentration of materials within the voxel (e.g. calcium, iodine), resulting in improved accuracy in e.g. perfusion imaging, kidney stone characterization, or bone density measurements 2

As of 2020, PCCT is not clinically available due to manifold technical challenges, primarily posed by cross-talk between the detector elements and the extremely fast detector readout required to separately count each incident x-ray photon 1-2

Imaging technology

Article information

rID: 78900
Synonyms or Alternate Spellings:
  • Photon-counting computed tomography (PCCT)

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