Performance evaluation of three different SPECT systems used in In-111 ProstaScint® SPECT imaging

The objective of this study was to evaluate the performance of 3 different SPECT systems for ¹¹¹In ProstaScint^® imaging. The systems were a Siemens E.CAM with 3/8" crystal fitted with a Siemens ME collimator, a GE Millennium VG5 with 5/8" and GE Discovery VH with 1" Starbrite^® crystal, both fitted with the same GE ME collimator. We compared the collimator-detector response (CDR) functions and sensitivity of the systems using an ¹¹¹In point source placed at different distances experimentally. Projection data were acquired from a cylindrical phantom and then the anthropomorphic torso phantom containing 3 ¹¹¹In-filled spheres of different sizes, and reconstructed with the OSEM algorithm. The radial and tangential FWHM of the spheres were compared. The sensitivity of the Siemens E.CAM was found to be higher than that of the GE VH due to the higher collimator efficiency despite the thinner crystal, and the sensitivity of the GE VH was higher than that of the GE VG5 due to its thicker crystal. The FWHM of the point source for the GE VG5 and VH systems was comparable since they share the same collimator and their crystals have comparable intrinsic resolution. The Siemens E.CAM had better resolution than the two GE systems at 10 cm, but was worse at 20 and 30 cm from the collimator, this is due to its shorter bore collimator design. The comparison of the FWHM of the larger spheres showed poorer resolution of the Siemens E. CAM as compared to the GE systems. The GE VH and GE VG5 systems gave comparable FWHM values, indicating comparable intrinsic resolution of the 5/8" continuous and the 1" Starbrite^® crystals. We conclude that, among the 3 collimator-camera systems, the GE VH provides a good compromise between spatial resolution and sensitivity for ¹¹¹In ProstaScint^® SPECT imaging.