Isotope specific resolution modelling image reconstruction for high resolution PET imaging

Measuring the spatially variant point spread function (PSF) on a PET scanner involves using a point source to sample the field of view (FOV) at multiple locations. However, since most clinically used isotopes have short half-lives, usually other non-clinically used long-lived isotopes are employed in practice. As such, due to the difference in positron range, non-optimal PSF models that do not correspond to those needed for the data to be reconstructed, are used within resolution modelling (RM) image reconstruction, usually underestimating the true PSF. In our previous work, the spatially variant PSF was measured on the HRRT based on clinically used isotopes. Here we extend the work by evaluating the impact of using isotope-specific PSF maps within RM image reconstruction. Evaluation is performed using point source, phantom and clinical datasets. Results suggest that further improvements in spatial resolution and contrast can be obtained by using an isotope-specific PSF.