Internal validation of myocardial flow reserve PET imaging using stress/rest myocardial activity ratios with Rb-82 and N-13-ammonia.

BACKGROUND

Myocardial flow reserve (MFR) measurement provides incremental diagnostic and prognostic information. The objective of the current study was to investigate the application of a simplified model for the estimation of MFR using only the stress/rest myocardial activity ratio (MAR) in patients undergoing rest-stress cardiac PET MPI.

METHODS AND RESULTS

Rest and dipyridamole stress dynamic PET imaging was performed in consecutive patients using Rb or NH (n = 250 each). Reference standard MFR was quantified using a standard one-tissue compartment model. Stress/rest myocardial activity ratio (MAR) was calculated using the LV-mean activity from 2 to 6 minutes post-injection. Simplified estimates of MFR (MFR) were then calculated using an inverse power function. For NH, there was good correlation between MFR and MFR values (R = 0.63), with similar results for Rb (R = 0.73). There was no bias in the MFR values with either tracer. The overall diagnostic performance of MFR for detection of MFR < 2 was good with ROC area under the curve (AUC) = 83.2 ± 1.2% for NH and AUC = 90.4 ± 0.7% for Rb.

CONCLUSION

MFR was estimated with good accuracy using Rb and NH with a simplified method that relies only on stress/rest activity ratios. This novel approach does not require dynamic imaging or tracer kinetic modeling. It may be useful for routine quality assurance of PET MFR measurements, or in scanners where full dynamic imaging and tracer kinetic modeling is not feasible for technical or logistical reasons.