Single-scan rest/stress imaging: validation in a porcine model with 18F-Flurpiridaz.

Abstract

18F-labeled myocardial flow agents are becoming available for clinical application but the ∼2hour half-life of 18F complicates their clinical application for rest-stress measurements. The goal of this work is to evaluate in a pig model a single-scan method which provides quantitative rest-stress blood flow in less than 15minutes. Single-scan rest-stress measurements were made using 18F-Flurpiridaz. Nine scans were performed in healthy pigs and seven scans were performed in injured pigs. A two-injection, single-scan protocol was used in which an adenosine infusion was started 4minutes after the first injection of 18F-Flurpiridaz and followed either 3 or 6minutes later by a second radiotracer injection. In two pigs, microsphere flow measurements were made at rest and during stress. Dynamic images were reoriented into the short axis view, and regions of interest (ROIs) for the 17 myocardial segments were defined in bull's eye fashion. PET data were fitted with MGH2, a kinetic model with time varying kinetic parameters, in which blood flow changes abruptly with the introduction of adenosine. Rest and stress myocardial blood flow (MBF) were estimated simultaneously. The first 12-14 minutes of rest-stress PET data were fitted in detail by the MGH2 model, yielding MBF measurement with a mean precision of 0.035ml/min/cc. Mean myocardial blood flow across pigs was 0.61 ± 0.11mL/min/cc at rest and 1.06 ± 0.19mL/min/cc at stress in healthy pigs and 0.36 ± 0.20mL/min/cc at rest and 0.62 ± 0.24mL/min/cc at stress in the ischemic area. Good agreement was obtained with microsphere flow measurement (slope = 1.061 ± 0.017, intercept = 0.051 ± 0.017, mean difference 0.096 ± 0.18ml/min/cc). Accurate rest and stress blood flow estimation can be obtained in less than 15min of PET acquisition. The method is practical and easy to implement suggesting the possibility of clinical translation.