Observer studies of cardiac lesion detectability with triple-head 360° vs. dual-head 180° SPECT acquisition using simulated projection data

The purpose of this study is to evaluate cardiac lesion detectability with triple-head 360-degree versus dual-head 180-degree myocardial perfusion SPECT scans with equal acquisition time. The channelized Hotelling observer (CHO) and human observers were used. A male and a female voxelized four-dimensional cardiac-torso phantoms were used to generate the 360-degree and the 180-degree projection data. A cold lesion was placed in 8 different locations of myocardium and had a lesion contrast of 25%. Sufficient poisson noise was added to set the area under the ROC curve (A_z) to be between 0.75 to 0.85 in a pilot study, and to simulate the clinical case where dual-head 180-degree and triple-head 360-degree both have the same total scan time. For each lesion location, 100 realizations of lesion present and of lesion-absent data were generated. Five iteration OSEM was used to reconstruct the data with no attenuation correction. A 3D Hann filter with 0.7 times the Nyquist frequency was used to smooth the reconstructed images. The CHO showed a higher lesion detectability index d´ for the 180-degree data. The human observer study showed a slightly better detection performance of the 180-degree scan, especially for the female phantom, but the differences were not statistically significant (at the P = 0.05 level)