What factors effect the resolution if CT images and PET images?

For CT I have come across a few, in terms of

  • Ray width
  • Dector aperture
  • focal spot

Which are common for most x-ray based scan as I understand, but are there more, would the voxel size effect the resolution?

For PET scan through research I have only come across what the account as error, which I suppose would effect the image quality/resolution which are

  • Scatter coincidence, or random coincidence
  • Position error, where the point rec annihilation on the LOR is not the true annihilation.
  • Particle energy error, so loss of energy through thermal processes.

I am also assuming as both detectors are sinitalltors then thickness of the crystal also effects the resolution.

Are there any more factors and do PET and CT share any common one apart from the crystal one that I have listed above?

  • $\begingroup$ How about the quantum photon noise that translates to the acquisition time? The fewer photons you have the more noisy the image is. $\endgroup$
    – safesphere
    Aug 10, 2018 at 20:28

1 Answer 1


For CT, neglecting any effects of patient motion, and in no particular order,

  • reconstruction matrix size
  • detector element size
  • focal spot size (relatively small effect)
  • acquisition sampling (how many rays you're using for the reconstruction)
  • reconstruction algorithm/kernel

For PET, again neglecting any effects of patient motion, and in no particular order

  • crystal element size and thickness
  • crystal temporal response
  • crystal type (BGO, LSO, etc)
  • coincidence timing window
  • energy of the emitted positrons
  • reconstruction algorithm/kernel

There might be others that I'm missing, but those would be the most significant ones.

Noise is not a factor in resolution. It will affect the detectability of objects, but doesn't affect resolution.


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