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Tests of a 3D visual-search model observer for SPECT

Observer studies with single 2D images can bias assessments of diagnostic technologies, as physicians usually have access to an entire image volume presented as multiple slices in multiple views. Previously, we introduced a scanning model observer for detection-localization tasks with multislice-multiview (or volumetric) display, but this observer did not compare well against human-observer data. The current work continues our investigation with tests of a 3D visual-search (VS) model observer. The VS framework amounts to an initial holistic search that identifies suspicious locations for analysis by a statistical observer. Our VS model uses a scanning observer for the analysis. The VS model was evaluated against the scanning and human observers in a localization ROC study of mass detection in SPECT lung imaging. The study compared two iterative reconstruction strategies that applied different combinations of corrections for attenuation, scatter, and distance-dependent system resolution. In our earlier work, the scanning and human observers ranked the strategies in opposite order of performance. The ranking from the VS observer matched that of the humans.