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

Abstract

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 82 Rb or 13 NH 3 (n\u2009=\u2009250 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 EST ) were then calculated using an inverse power function. For 13 NH 3 , there was good correlation between MFR and MFR EST values ( R \u2009=\u20090.63), with similar results for 82 Rb ( R \u2009=\u20090.73). There was no bias in the MFR EST values with either tracer. The overall diagnostic performance of MFR EST for detection of MFR\u2009<\u20092 was good with ROC area under the curve (AUC)\u2009=\u200983.2\u2009±\u20091.2% for 13 NH 3 and AUC\u2009=\u200990.4\u2009±\u20090.7% for 82 Rb. Conclusion MFR was estimated with good accuracy using 82 Rb and 13 NH 3 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.