Evaluation of the Usefulness of the Myocardial Flow Reserve Index Using an Anger-Type SPECT/CT System

Background: The quantitative analysis of myocardial blood flow and myocardial flow reserve (MFR) is expected to address challenges in evaluating the relative distribution of myocardial perfusion imaging. This study aimed to determine the normal range of MFR index using the myocardial uptake ratio (MUR) method in normal volunteers (NV) with an Anger-type single photon emission computed tomography/computed tomography (SPECT/CT) system and to evaluate its diagnostic accuracy for ischemic heart disease (IHD) and heart failure (HF). Methods: Two methods for calculating the MUR were evaluated. The area under the curve (AUC) method utilized the AUC of the time-activity curve (TAC) of the aortic arch as the input function (AUC-based MFR index). The DOSE method employed the dose activity (dose-based MFR index). IHD was categorized into single-vessel disease (SVD) and multivessel disease (MVD; double- and triple-vessel disease combined). Results: Normal range of AUC-based MFR index was 1.63 ± 0.30, 1.40 ± 0.24 for SVD, 1.28 ± 0.17 for MVD, and 1.11 ± 0.12 for HF. The normal range of the dose-based MFR index was 1.18 ± 0.14, 1.15 ± 0.26 for SVD, 1.02 ± 0.10 for MVD, and 0.99 ± 0.06 for HF. Significant differences were observed among the NV, MVD, and HF groups. No significant differences were noted between NV and SVD groups. The results of the receiver operating characteristic curve (ROC) analysis in combination with NV showed that the AUC of the ROC curve was 0.732 (95%CI 0.542-0.922) for SVD, 0.841 (95%CI 0.717-0.965) for MVD, and 0.969 (95%CI, 0. 922-1.0) for HF. The AUC of dose-based MFR index were 0.667 (95%CI 0.404-0.929) for SVD, 0.817 (95%CI 0.684-0.950) for MVD, and 0.908 (95%CI 0.814-1.0) for HF. DeLong's test showed no significant differences between the AUC of AUC-based and dose-based MFR indices. Conclusion: The findings suggest the potential clinical application of AUC and DOSE methods for quantitative analysis of the MFR index using an Anger-type SPECT/CT system. These methods are expected to enhance the accuracy of diagnosis and prognosis in patients with IHD and HF.