Feasibility and operator variability of myocardial blood flow and reserve measurements with ⁹⁹mTc-sestamibi quantitative dynamic SPECT/CT imaging.

PURPOSE: Myocardial blood flow (MBF) quantification with dynamic SPECT could lead to widespread utilization of MBF imaging in clinical practice with little cost increase over current standard SPECT myocardial perfusion imaging. This work evaluates the feasibility and operator-dependent variability of MBF and flow reserve measurements with (99m)Tc-sestamibi (MIBI) dynamic SPECT imaging using a standard dual-head SPECT camera.

METHODS: Twenty-eight patients underwent dipyridamole-stress and rest imaging with dynamic SPECT/CT acquisition. Quantitative images were iteratively reconstructed with all physical corrections and then myocardial and arterial blood regions of interest (ROI) were defined semi-automatically. A compartmental model was fitted to these ROI-sampled time-activity-curves, and flow-dependent MIBI extraction correction was applied to derive regional MBF values. Myocardial flow reserve (MFR) was estimated as stress/rest MBF ratio. MBF and MFR in low and high risk populations were evaluated for ability to detect disease. Images were each processed twice (≥7 days apart) by one expert and one novice operator to evaluate intra- and inter-operator variability of MBF and MFR measurement in the three coronary artery vascular territories.

RESULTS: Mean rest flow, stress flow, and MFR values were 0.83, 1.82 mL·minute(-1)·g(-1), and 2.45, respectively. For stress/rest MFR, the inter-operator reproducibility was r(2) = 0.86 with RPC = 1.1. Stress MBF and MFR were significantly reduced (P < .05) in high risk (n = 9) vs low risk populations (n = 19), indicating ability to detect disease. For expert and novice operators very good intra-operator correlations of r(2) = 0.98 and 0.95 (n = 168, P < .001) were observed for combined rest and stress regional flow values. Bland-Altman reproducibility coefficients (RPC) were 0.25 and 0.47 mL·minute(-1)·g(-1) for the expert and novice operators, respectively (P < .001). Inter-operator correlation was r(2) = 0.91 and Bland-Altman RPC = 0.58 mL·minute(-1)·g(-1) (n = 336).

CONCLUSIONS: MBF and reserve measurements using (99m)Tc-sestamibi on a traditional, two-headed camera with fast rotation and with quantitative dynamic SPECT appears to be feasible, warranting further investigation.