Comparison of static and dynamic cardiac perfusion thallium-201 SPECT

Clinically, cardiac SPECT is performed 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. To make this comparison, canine studies were performed each with an occlusion placed on a 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 estimates were used as the gold standard. The dynamic data were fit to a two-compartment model to provide regional estimates of washin rate parameters. Occluded to normal ratios were also calculated for each study. Preliminary results show comparable correlations with microspheres for both washin and static scaled image intensities. In addition, dynamic data provided higher defect contrasts which were more accurate than the static occluded to normal ratios, using microspheres-derived flows as the standard. These results show promise for dynamic thallium imaging to provide improved information contrast compared to static imaging for myocardial perfusion SPECT studies.