Spatially variant point spread function for PET rigid motion correction

Positron emission tomography (PET) scanners usually present a spatially variant loss of spatial resolution. In addition, in scans where the subject can move across the scanner field of view (FOV), e.g. scans of freely moving animals, the loss of spatial resolution is motion dependent. The scanner spatially variant point spread function (SVPSF) can be estimated and then the loss of spatial resolution can be compensated by using resolution modeling. For motion correction reconstruction incorporating resolution modeling, the motion dependence of the SVPSF needs to be considered. Here we propose a method to calculate the motion dependent and spatially variant PSF for resolution modeling in motion correction reconstruction, using an asymmetric Gaussian model for the SVPSF. The SVPSF using the asymmetric Gaussian model produced a more uniform spatial resolution over the entire scanner FOV. Compared to a spatially invariant Gaussian model, the motion dependent SVPSF produced improved spatial resolution in motion corrected reconstructions of a resolution phantom. Using the motion dependent SVPSF in motion correction reconstruction improves spatial resolution and quantification in PET reconstructions. Therefore, scans of freely moving animal can benefit from using this method.