Impact of depth-of-interaction on image resolution in long axial-FOV PET

In whole body PET scanners, extending the axial field of view (AFOV) can significantly increases the sensitivity. However, image axial resolution, which is an essential criterion in whole-body PET, may be especially affected by the depth of interaction (DOI) as the AFOV increases. In this paper, we use Monte Carlo simulations to find, in a long axial-FOV PET how DOI information affects the axial resolution. We also compared the axial resolution in scanners with only different AFOV ranging from 158 mm to 360 mm. All axial resolutions were measured as a function of ring difference (sensitivity) both with and without DOI information. The simulation study shows that as AFOV increases the axial spatial resolution gets worse much more quickly compared with that in transverse direction and in the scanner with largest AFOV (360 mm), introduction of DOI improves axial resolution by 12.28%. Besides, the introduction of DOI information can significantly increase the sensitivity performance by up to 37.5% when the axial resolution is fixed to 1cm because a DOI PET system allows more oblique events to be used in the image reconstruction.