Photon depth of interaction in various scintillation crystals and its influence on PET image spatial resolution

In a PET imaging system, the annihilation photon depth of interaction (DOI) in the scintillator introduces a detection parallax error that contributes to image blurring. Its contribution on the image spatial resolution was theoretically investigated by Monte Carlo calculations of the three dimensional photon transport within a given scintillator (BGO, LSO, LuAP, GSO, NaI) and for a given PET detector geometry in both 2D and 3D registration mode. In addition the uncertainty due to the emission photon non-colinearity (NC) was also included in the calculation.