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RATIONALE AND OBJECTIVES. Single photon emission computed tomography (SPECT) with a cone–beam collimator improves the trade-off between detection efficiency and spatial resolution for cardiac imaging. However, acquisitions using orbits where the focus remains in a plane do not provide sufficient data for exact reconstruction. In the current study the authors evaluate the clinical utility of planar-orbit cone–beam SPECT in detecting a simple myocardial defect.METHODS. Observer performance experiments compared high-resolution cone–beam with same-resolution parallel-hole and fan–beam collimator designs in myocardial defect detection using a computer-simulated cardiac model. The uptake of Thallium-201 in the myocardium and other tissue organs was modeled by a mathematical three-dimensional upper torso phantom from which physically realistic projections were simulated. Eight observers viewed reconstructed transaxial images from the three collimator designs and indicated the certainty with which they detected a Gaussian-shaped defect at a specified location.RESULTS. The area under the receiver operating characteristic curve indicated that the cone–beam design, regardless of slice position, was superior to the fan–beam, which in turn was superior to the parallel-hole design for the specified detection task.CONCLUSIONS. The observer study demonstrated that reconstruction artifacts resulting from insufficient data sampling do not binder obtaining improved diagnostic information from planar-orbit cone–beam cardiac SPECT images compared to conventional cardiac SPECT using parallel-hole and fan–beam collimators.