LROC analysis of detector-response compensation in SPECT

Localization ROC (LROC) observer studies examined whether detector response compensation (DRC) in ordered-subset, expectation-maximization (OSEM) reco nstructions helps in the detection and localization of hot tumors. Simulate d gallium (Ga-67) images of the thoracic region were used in the study, The projection data modeled the acquisition of attenuated 93- and 185-keV phot ons with a medium-energy parallel-hole collimator, but scatter was not mode led, Images were reconstructed with five strategies: 1) OSEM with no DRC; 2 ) OSEM preceded by restoration filtering; 3) OSEM with iterative DRC; 4) OS EM with an ideal DRC; and 5) filtered backprojection (FBP) with no DRC, All strategies included attenuation correction. There were four LROC studies c onducted, In a study using a single tumor activity, the ideal DRC offered t he best performance, followed by iterative DRC, restoration filtering, OSEM with no DRC, and FBP, Statistical significance at the 5% level was found b etween all pairs of strategies except for restoration filtering and OSEM wi th no DRC, A similar ranking was found for a more realistic study using mul tiple tumor activities. Additional studies considered the effects of OSEM i teration number and tumor activity on the detection improvement that iterat ive DRC offered with respect to OSEM with no DRC.