Perivascular Fat Attenuation Index on Non-Contrast-Enhanced Cardiac Computed Tomography: Comparison with Coronary Computed Tomography Angiography

Objective: Perivascular fat attenuation index (FAI) measurement on non-contrast-enhanced cardiac computed tomography (NCCT) has not been rigorously validated in previous studies. Herein, we compared perivascular FAI values between NCCT and coronary computed tomography angiography (CCTA). We also investigated the variability and reproducibility of perivascular FAI measurement. Methods: A total of 44 patients who underwent NCCT and CCTA were included in this study. For NCCT, perivascular FAI was measured using three threshold settings: from −30 to −190 Hounsfield Units (HU), −20 to −180 HU, and −10 to −170 HU. For CCTA, perivascular FAI was measured using one threshold setting: from −30 to −190 HU. Perivascular FAI measurements by NCCT were compared with those by CCTA using the paired t-test, and correlations were assessed using Pearson’s correlation coefficient. The intra- and inter-observer variabilities for the measurements with NCCT and CCTA were evaluated with the intraclass correlation coefficient. Results: Perivascular FAI measurements with the threshold setting of −30 to −190 HU were significantly lower on NCCT than on CCTA. There were no significant differences between the perivascular FAI measurements at the remaining thresholds on NCCT and those on CCTA. The perivascular FAI at all thresholds on NCCT correlated significantly with those on CCTA. The intra- and inter-observer agreements were excellent for the measurements on NCCT and CCTA. Conclusion: There were significant differences between the perivascular FAI measurements on NCCT and CCTA. However, the differences could be modified by threshold adjustment.