Contrast-enhanced cardiac MR imaging in the detection of reduced coronary flow velocity reserve

Purpose: To prospectively evaluate the accuracy of contrast material-enhanced cardiac magnetic resonance ( MR) imaging for determining impaired coronary flow velocity reserve ( CFR) by using Doppler flow measurement as the reference standard. Materials and Methods: The study was approved by the institutional ethics committee, and all patients gave written informed consent. Eligible patients underwent contrast-enhanced cardiac MR imaging and invasive measurement of CFR. For contrast-enhanced MR imaging, a three-section single-shot saturation recovery gradient-recalled echo sequence with steady-state free precession was used. Sections were divided into six segments. For each segment, a transmural and subendocardial myocardial perfusion reserve index ( MPRI)was calculated by using the upslope of the signal intensity-time curve during the first pass of contrast material at rest and during adenosine infusion ( 140 mu g per kilogram body weight per minute). MPRIs of vascular regions were compared with the corresponding CFR. Receiver operating characteristic ( ROC) analysis was performed to find the number of segments needed for best diagnostic accuracy of MPRI and to find a cutoff value for MPRI in the detection of a reduced CFR. Results: Thirty-five patients were evaluated ( male-to-female ratio, 27: 8; mean age +/- standard deviation, 63.5 years +/- 8.2; mean body mass index, 28.8 kg/m(2) +/- 3.8), and 43 vascular regions were analyzed. A linear correlation was found between the MPRI and CFR ( r = 0.44, P <.05). The MPRI was significantly lower in vascular regions with a CFR of less than 2.00 than in regions with a CFR of 2.00 or greater ( P <.05). Detection of a CFR of less than 2.00 was more accurate with subendocardial MPRI measurements than with transmural measurements. The mean subendocardial MPRI of the segments with the three lowest MPRIs of a vascular region showed the best diagnostic performance in the detection of a CFR of less than 2.00 ( area under the ROC curve, 0.85; sensitivity, 84%; specificity, 75%) by using a cutoff value of 1.21. Conclusion: The diagnostic accuracy of subendocardial perfusion analysis in contrast-enhanced cardiac MR imaging is higher than that of transmural analysis. (c) RSNA, 2007.