Static Versus Dynamic Teboroxime Myocardial Perfusion SPECT in Canines

Abstract

Tc-99m-teboroxime is a perfusion tracer with high myocardial extraction, fast washin and washout kinetics, and excellent imaging properties. The fast kinetics pose some problems for static imaging, but they also allow for back-to-back stress / rest studies to be performed very quickly. Furthermore, such fast kinetics are ideally suited for dynamic imaging. We have compared static versus dynamic myocardial perfusion SPECT with teboroxime in canines using microsphere-derived flow values as the gold standard. Dynamic data were successfully acquired at rest and under adenosine stress in seven dogs using a fast serial scanning protocol. The data were analyzed in two ways: summing timeframes to create a single, static dataset with consistent projections; and 4D reconstruction and kinetic parameter estimation for a two compartment model. In both cases imaging data (voxel intensity or washin rate parameter) were correlated with flow values measured by microspheres. The static summing procedure that produced the best correlation with flow consisted of summing the projection data acquired from 60 to 180 seconds post-injection. The washin rate parameter was found to provide better correlation with flow than static image intensity in six of seven animals. When the data were pooled over all studies, washin provided significantly better correlation with flow than static imaging (p<0.01). We conclude that dynamic imaging of teboroxime with compartmental modeling provides a better measure of flow than can be obtained from static imaging techniques.

Figure 1

A two-compartment model for the exchange of teboroxime between the blood and extravascular myocardial tissue.

Figure 2

Mean correlation coefficient for static image intensity vs. blood flow in all studies shown as a function of summed static scan duration and delay post-injection.

Figure 3

Reconstructed short-axis slices for one of the stress studies for summed static data of 2 minutes (top row) and 5 minutes (bottom row) duration. A delay of 1 minute post-injection was used. Note that the noise levels in both sets of images appear similar.

Figure 4

Sample time-activity curves for one of the stress studies. The fitted washin and washout parameters are shown.

Figure 5

Correlation plots of SPECT imaging results vs. microsphere-derived flows showing data pooled for all studies: unscaled washin parameter k₂₁ (top), inter-study scaled washin parameter k₂₁ (middle), and scaled static image intensity (bottom). The fitted regression lines are also shown for each case.