Rubidium-82 PET-CT for quantitative assessment of myocardial blood flow: validation in a canine model of coronary artery stenosis

Abstract

Absolute quantification of myocardial blood flow expands the diagnostic potential of PET for assessment of coronary artery disease. (82)Rb has significantly contributed to increasing utilization of PET; however, clinical studies are still mostly analysed qualitatively. The aim of this study was to reevaluate the feasibility of (82)Rb for flow quantification, using hybrid PET-CT in an animal model of coronary stenosis. Nine dogs were prepared with experimental coronary artery stenosis. Dynamic PET was performed for 8 min after (82)Rb(1480-1850 MBq) injection during adenosine-induced vasodilation. Microspheres were injected simultaneously for reference flow measurements. CT angiography was used to determine the myocardial regions related to the stenotic vessel. Two methods for flow calculation were employed: a two-compartment model including a spill-over term, and a simplified retention index. The two-compartment model data were in good agreement with microsphere flow (y = 0.84x + 0.20; r = 0.92, p<0.0001), although there was variability in the physiological flow range <3 ml/g per minute (y = 0.54x + 0.53; r = 0.53, p = 0.042). Results from the retention index also correlated well with microsphere flow (y = 0.47x + 0.52; r = 0.75, p = 0.0004). Error increased with higher flow, but the correlation was good in the physiological range (y = 0.62x + 0.29; r = 0.84, p = 0.0001). Using current state-of-the-art PET-CT systems, quantification of myocardial blood flow is feasible with (82)Rb. A simplified approach based on tracer retention is practicable in the physiological flow range. These results encourage further testing of the robustness and usefulness in the clinical context of cardiac hybrid imaging.