Sahar Rezaei1,2 · Pardis Ghafarian3,4 · Mehrdad Bakhshayesh‑Karam3,4 · Carlos F. Uribe5 · Arman Rahmim6,7 · Saeed Sarkar2 · Mohammad Reza
Objectives The present study aims to assess the impact of acquisition time, diferent iterative reconstruction protocols as well as image context (including contrast levels and background activities) on the measured spatial resolution in PET images.
Methods Discovery 690 PET/CT scanner was used to quantify spatial resolutions in terms of full width half maximum (FWHM) as derived (i) directly from capillary tubes embedded in air and (ii) indirectly from 10 mm-diameter sphere of the NEMA phantom. Diferent signal-to-background ratios (SBRs), background activity levels and acquisition times were applied. The emission data were reconstructed using iterative reconstruction protocols. Various combinations of iterations and subsets (it×sub) were evaluated.
Results For capillary tubes, improved FWHM values were obtained for higher it×sub, with improved performance for PSF algorithms relative to non-PSF algorithms. For the NEMA phantom, by increasing acquisition times from 1 to 5 min, intrinsic FWHM for reconstructions with it×sub 32 (54) was improved by 15.3% (13.2%), 15.1% (13.8%), 14.5% (12.8%) and 13.7%
(12.7%) for OSEM, OSEM+PSF, OSEM+TOF and OSEM+PSF+TOF, respectively. Furthermore, for all reconstruction protocols, the FWHM improved with more impact for higher it×sub.
Conclusion Our results indicate that PET spatial resolution is greatly afected by SBR, background activity and the choice of the reconstruction protocols.
Keywords Positron emission tomography · FWHM · Spatial resolution · Iterative reconstruction · TOF · PSF