Simultaneous acquisition Positron Emission Tomography/Magnetic Resonance (PET/MR) is a new technology with potential use in cardiac perfusion imaging. Pharmacologic stress perfusion imaging with 13N-ammonia-PET and MR have previously been validated separately for detection of coronary artery disease (CAD). In this pilot study, we optimize a protocol for comprehensive cardiac PET/MR stress perfusion imaging, and evaluate its diagnostic accuracy for CAD when compared to GSPECT-MPI.
METHOD AND MATERIALS15 patients with reversible myocardial perfusion defect on GSPECT-MPI for whom standard of care coronary angiography was planned were recruited. Patients received 400mcg Regadenoson, followed 30 seconds later by simultaneous 13N-Ammonia-PET (10.2 +/- 0.46 mCi) and gadolinium-based (0.075 mmol/Kg) contrast MR perfusion imaging. The procedure was repeated at rest. PET attenuation correction µ-map was a dual echo VIBE Dixon sequence. PET images were reconstructed with 3D-OSEM (Ordered Subset Estimation Maximization) with 3 iterations, 21 subsets and post-Gaussian filter of 4 mm. The presence and absence of ischemia and infarction were assessed by two independent readers. Areas of decreased perfusion on MRI were correlated to PET myocardial blood flows (MBF) as measured by 2-compartment modeling analysis.
RESULTSPET/MR demonstrated excellent concordance with coronary angiographic findings. In this small data set, when compared to GSPECT-MPI, combined PET/MR demonstrated superior diagnostic accuracy (69% vs 54%). The inter-reader concordance was 77%. Using PET/MR as a diagnostic tool for CAD, in this small cohort, there is a 100% sensitivity, 100% negative predictive value, and a 64% positive predictive value.
CONCLUSIONEarly experience with 13N-PET/MR perfusion imaging showed excellent diagnostic accuracy, sensitivity and specificity for CAD detection.
CLINICAL RELEVANCE/APPLICATIONPerfusion PET/MR offers a comprehensive myocardial ischemic evaluation. Potential benefits including shorter exam time than SPECT, lower radiation dose, absolute myocardial blood flow quantification, and internal validation between PET and MR findings.