Comparison of Static and Dynamic Cardiac Perfusion Thallium-201 SPECT

Cardiac SPECT is typically performed clinically with static imaging protocols and visually assessed for perfusion defects based upon the relative intensity of myocardial regions. Dynamic imaging, however, has the potential to provide quantitative measures of flow, possibly improving diagnosis. The objective of this study was to compare the information content of dynamic and static thallium SPECT imaging as measures of myocardial perfusion. Studies were performed in four canines, each with an occlusion placed on the left anterior descending coronary artery. Dynamic SPECT imaging was performed at rest and under adenosine stress, and subsets of the data were summed to provide corresponding static datasets for identical physiologic conditions. Microsphere-derived flow measurements were used as the gold standard. The dynamic data were fit to a two-compartment model to provide regional estimates of wash-in rate parameters. Occluded-to-normal ratios were also calculated for each canine study. The results show comparable correlations with microspheres for both wash-in and static scaled image intensities. The dynamic data provided higher defect contrasts, which were more accurate than the static occluded to normal ratios. Preliminary studies were also performed in two patients and the static and dynamic data compared. These results show that dynamic thallium imaging may provide improved diagnostic information compared to static imaging for myocardial perfusion SPECT studies.