The novel PET flow tracer flurpiridaz F 18 shows high myocardial extraction and slow washout. flurpiridaz F 18 PET data analysis with tracer kinetic modeling provides accurate absolute myocardial blood flow (MBF) measurements but requires in-scanner injection and complex processing. We evaluated the hypothesis that myocardial retention and standardized uptake values (SUVs) based on late uptake provide accurate estimates of myocardial flow reserve (MFR) and, thus, might allow simplified quantification after tracer injection outside the scanner. Methods: Nine pigs had dynamic PET scans after repeated injections of flurpiridaz F 18 at rest and combined adenosine and dobutamine stress. flurpiridaz F 18 PET with a 3-compartment model and coinjected radioactive microspheres were used to delineate MBF. These quantitative measurements were compared with myocardial retention (%/min) and SUV of flurpiridaz F 18 after summing data over 5-10, 5-12, 5-15, 10-15, and 10-20 min after tracer injection. Results: MBF ranged from 0.5 to 2.8 mL/min/g. There was a good correlation between both flurpiridaz F 18 retention and SUVs from 5 to 12 min after injection and MBF measured using 3-compartment modelor microsphere-derived MBF (r 5 0.73, P , 0.05, and r 5 0.68, P , 0.05, respectively, for retention; r 5 0.88, P , 0.001, and r 5 0.92, P , 0.001, respectively, for SUV). At later time points, retention and SUV underestimated stress microsphere flow (at 10-20 min: r 5 0.41, P 5 not significant, and r 5 0.46, P 5 not significant, respectively, for retention; r 5 0.41, P 5 not significant, and r 5 0.65, P , 0.05, respectively, for SUV). When measured 5-12 min after injection, there was a close agreement between MFR measured with either flurpiridaz F 18 retention or SUV and MFR measured using microspheres (mean difference, 20.08 6 0.36 and 20.18 6 0.25, respectively). Conclusion: Myocardial retention and SUVs of the 18 F-labeled flow tracer flurpiridaz F 18 accurately reflect the MFR. These simplified analysis methods may facilitate the combination of quantitative assessment of perfusion reserve and rapid clinical imaging protocols. Myocardi al perfusion imaging with SPECT and PET is a standard tool for detection of coronary artery disease, risk stratification of patients, and guidance of therapeutic interventions (1-4). Usually, myocardial perfusion is analyzed in a qualitative manner, so that only relative perfusion changes can be detected. Absolute quantification of myocardial blood flow (MBF) and the subsequent calculation of myocardial flow reserve (MFR; the ratio of MBF at stress and rest) are a goal of essentially all invasive and noninvasive imaging approaches (4-8). Compared with qualitative analysis, quantitative assessment of perfusion can improve the accuracy with which coronary artery disease is detected. It can reduce the number of false-negative results in patients with multivessel disease, for which qualitative analysis often cannot uncover globally reduced perfusion or uncovers only the coronary territory supplied by the...