Quantification of absolute myocardial perfusion in patients with coronary artery disease: comparison between cardiovascular magnetic resonance and positron emission tomography

Abstract

Objectives: The aim of this study was to compare fully quantitative cardiovascular magnetic resonance (CMR) and positron emission tomography (PET) myocardial perfusion and myocardial perfusion reserve (MPR) measurements in patients with coronary artery disease (CAD).

Background: Absolute quantification of myocardial perfusion and MPR with PET have proven diagnostic and prognostic roles in patients with CAD. Quantitative CMR perfusion imaging has been established more recently and has been validated against PET in normal hearts. However, there are no studies comparing fully quantitative CMR against PET perfusion imaging in patients with CAD.

Methods: Forty-one patients with known or suspected CAD prospectively underwent quantitative (13)N-ammonia PET and CMR perfusion imaging before coronary angiography.

Results: The CMR-derived MPR (MPR(CMR)) correlated well with PET-derived measurements (MPR(PET)) (r = 0.75, p < 0.0001). MPR(CMR) and MPR(PET) for the 2 lowest scoring segments in each coronary territory also correlated strongly (r = 0.79, p < 0.0001). Absolute CMR perfusion values correlated significantly, but weakly, with PET values both at rest (r = 0.32; p = 0.002) and during stress (r = 0.37; p < 0.0001). Area under the receiver-operating characteristic curve for MPR(PET) to detect significant CAD was 0.83 (95% confidence interval: 0.73 to 0.94) and for MPR(CMR) was 0.83 (95% confidence interval: 0.74 to 0.92). An MPR(PET) ≤1.44 predicted significant CAD with 82% sensitivity and 87% specificity, and MPR(CMR) ≤1.45 predicted significant CAD with 82% sensitivity and 81% specificity.

Conclusions: There is good correlation between MPR(CMR) and MPR(PET.) For the detection of significant CAD, MPR(PET) and MPR(CMR) seem comparable and very accurate. However, absolute perfusion values from PET and CMR are only weakly correlated; therefore, although quantitative CMR is clinically useful, further refinements are still required.

Figure 1. Scatter Plots Comparing CMR- and PET-Derived MPR

Scatter plots with fit lines comparing myocardial perfusion reserve (MPR) values from cardiac magnetic resonance (MPR_CMR) and positron emission tomography (MPR_PET) for the entire myocardial territory (A) and the mean of the lowest 2 segments in each territory (MPR2) (B).

Figure 2. Agreement Between CMR and PET MPR

Bland-Altman plot showing the agreement between CMR- and PET-derived absolute MPR measurements. Abbreviations as in Figure 1.

Figure 3. I Correlation and Agreement Between CMR- and PET-Derived Absolute Perfusion Values

Scatter plots illustrating the correlation between absolute measures of myocardial perfusion at rest (A) and during peak stress (C), along with the corresponding Bland-Altman plots (B and D, respectively) with limits of agreement lines (2 SDs). CMR = cardiac magnetic resonance; PET = positron emission tomography.

Figure 4. Diagnosis of Significant CAD on Angiography With Quantitative CMR- and PET-Derived MPR

Mean myocardial perfusion reserve (MPR) of the lowest 2 segments (MPR2) in remote (<70%) and stenotic (≥70%) territories. The best cutoff values for the detection of coronary artery disease (CAD) (MPR_CMR 1.45 and MPR_PET 1.44) are shown. CMR = cardiac magnetic resonance; PET = positron emission tomography.

Figure 5. Case Example

Positron emission tomography (PET) (top), cardiac magnetic resonance (CMR) (middle), and the x-ray angiogram of the left coronary artery of a 54-year-old patient with diabetes and exertional angina. Basal, mid, and apical slices have been taken from the PET study, which approximately correspond to the CMR slices. There is a stress-induced perfusion defect in the infero-lateral region from base to apex visible on both PET and CMR images. There is a corresponding severe (>95%) stenosis of the proximal circumflex artery. There was no other significant angiographic disease. Myocardial perfusion reserve of the lowest 2 segments (MPR2) for each territory are shown in the table. The MPR2 for the circumflex artery (CX) is below the cutoff of 1.44 and 1.45 for both PET and CMR, respectively. LAD = left anterior descending artery; RCA = right coronary artery.