Comparing filtered backprojection and ordered-subsets expectation maximization for small-lesion detection and localization in Ga-67 SPECT

Iterative reconstruction of SPECT images has recently become clinically ava ilable as an alternative to filtered backprojection (FBP). However, there i s conflicting evidence on whether iterative reconstruction, such as with th e ordered-subsets expectation maximization (OSEM) algorithm, improves diagn ostic performance over FBP. The study objective was to determine if the det ection and localization of small lesions in simulated thoracic gallium SPEC T images are better with OSEM reconstruction than with FBP, both with and w ithout attenuation correction (AC). Methods: Images were simulated using an analytic projector acting on the mathematic cardiac torso computer phantom . Perfect scatter rejection was assumed. Lesion detection accuracy was asse ssed using localization receiver operating characteristic methodology. The images were read by 5 nuclear medicine physicians. For each reconstruction strategy and for each observer, data were collected in 2 viewing sessions o f 100 images. Two-way ANOVA and, when indicated, the Scheffe multiple compa risons test were applied to check for significant differences. Results: Lit tle difference in the accuracy of detection or localization was seen betwee n FBP with and without AC. OSEM with AC extended the contrast range for acc urate lesion detection and localization over that of the other methods inve stigated. Without AC, no significant difference between OSEM and FBP recons truction was detected. Conclusion: OSEM with AC may improve the detection a nd localization of thoracic gallium-labeled lesions over FBP reconstruction .