Feasibility of absolute flow quantification using dynamic thallium-201 myocardial perfusion SPECT on a CZT camera: a preliminary study

Objectives: Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) is greatly limited by its relative nature, especially in the presence of multi-vessel or diffuse coronary artery disease (CAD). The recently introduced cadmium-zinc-telluride (CZT) cardiac camera allows flow quantification from dynamic acquisition, which may overcome this issue. Despite the inferior physical property, Tl-201 has higher myocardial extraction fraction and flow linearity than either Tc-99m sestamibi or Tc-99m tetrofosmin. The aim of this study is to assess the feasibility of dynamic thallium SPECT in the clinical setting to detect obstructive CAD.

Methods: We prospectively recruited 165 consecutive patients referred for Tl-201 MPI. Half of the Tl-201 dose was administered at peak dipyridamole stress, and the other half was injected before the redistribution scan. Three-minute dynamic acquisition with list-mode storage was performed during tracer injection. An additional one-minute scan was performed before resting dynamic acquisition for background myocardial activity correction. Dynamic images were spliced and reconstructed into 5-second frames. The arterial input function was estimated by placing a volume of interest (VOI) at aortic root. Myocardial VOIs were automatically delineated by computer software. An one-tissue compartment model was used to estimate flow parameters for global myocardium and each vessel territory. Among these patients, we identified the subset of patients with subsequent coronary angiography for analysis. And we correlate the flow parameters with the angiographic findings.

Results: Total 22 patients with subsequent coronary angiography were identified. The prevalence of CAD in this population was 77%, while only 8 patients have obstructive disease (more than 70%). The post-stress myocardial blood flow (MBF) and coronary flow reserve (CFR) decreased as the number of involved vessels increased, while there is no obvious trend in resting myocardial blood flow (table 1). The vessel-based analysis showed significant lower myocardial blood flow (1.51 vs. 2.32, p<0.001) and coronary flow reserve (1.52 vs. 2.36, p=0.019) in obstructive vessel territories.

Conclusion: Absolute flow quantification using dynamic Tl-201 myocardial SPECT is clinically feasible by using a CZT camera. The stress-myocardial blood flow and coronary flow reserve are correlated with angiographic findings. Research Support: n/a