Reproducibility and Accuracy of Quantitative Myocardial Blood Flow Assessment with 82Rb PET: Comparison with 13N-Ammonia PET

Rb-82 cardiac PET allows the assessment of myocardial perfusion with a column generator in clinics that lack a cyclotron. There is evidence that the quantitation of myocardial blood flow (MBF) and coronary flow reserve (CFR) with dynamic Rb-82 PET is feasible. The objectives of this study were to determine the accuracy and reproducibility of MBF estimates from dynamic Rb-82 PET by using our methodology for generalized factor analysis (generalized factor analysis of dynamic sequences [GFADS]) and compartment analysis. Methods: Reproducibility was evaluated in 22 subjects undergoing dynamic rest and dipyridamole stress Rb-82 PET studies at a 2-wk interval. The inter-and intraobserver variability of MBF quantitation with dynamic Rb-82 PET was assessed with 4 repeated estimations by each of 4 observers. Accuracy was evaluated in 20 subjects undergoing dynamic rest and dipyridamole stress PET studies with Rb-82 and N-13-ammonia, respectively. The left ventricular and right ventricular blood pool and left ventricular tissue time-activity curves were estimated by GFADS. MBF was estimated by fitting the blood pool and tissue time-activity curves to a 2-compartment kinetic model for Rb-82 and to a 3-compartment model for N-13-ammonia. CFR was estimated as the ratio of peak MBF to baseline MBF. Results: The reproducibility of the MBF estimates in repeated Rb-82 studies was very good at rest and during peak stress (R-2 = 0.935), as was the reproducibility of the CFR estimates (R-2 = 0.841). The slope of the correlation line was very close to one for the estimation of MBF (0.986) and CFR (0.960) in repeated Rb-82 studies. The intraobserver reliability was less than 3% for the estimation of MBF at rest and during peak stress as well as for the estimation of CFR. The interobserver reliabilities were 0.950 at rest and 0.975 at peak stress. The correlation between myocardial flow estimates obtained at rest and those obtained during peak stress in Rb-82 and N-13-ammonia studies was very good (R-2 = 0.857). Bland-Altman plots comparing CFR estimated with Rb-82 and CFR estimated with N-13-ammonia revealed an underestimation of CFR with Rb-82 compared with N-13-ammonia; the underestimation was within 61.96 SD. Conclusion: MBF quantitation with GFADS and dynamic Rb-82 PET demonstrated excellent reproducibility as well as intra- and inter-observer reliability. The accuracy of the absolute quantitation of MBF with factor and compartment analyses and dynamic Rb-82 PET was very good, compared with that achieved with N-13-ammonia, for MBF of up to 2.5 mL/g/min.