Measurement of Epicardial Fat Using Non-contrast Routine Chest-CT: A Consideration of Threshold Adjusting for Fatty Attenuation

Abstract Background：Role of epicardial fat (EF) had expended from a marker of cardiovascular risk to indicators of several systemic physiological effects and needed to be measured in more scenarios. The present study aimed to determine whether the EF volume (EFV) and mean attenuation (EFA) measured on non-contrast routine chest-CT (RCCT) could be more consistent with that on coronary CT angiography (CCTA) by adjusting the threshold of fatty attenuation. Methods: Totally 83 subjects simultaneously underwent CCTA and RCCT were enrolled. EFV and EFA were quantified on CCTA using threshold of (N30) (-190HU, -30HU) as reference, and also measured on RCCT using threshold of N30, N40 (-190HU, -40HU), N45 (-190HU, -45HU) respectively. Correlation and agreement of EF metrics between two models and differences between groups with coronary plaque (Plaque (+)) and without plaque (Plaque (-)) were analyzed. Results: EFV and EFA from RCCT using N30, N40 and N45 correlated well with reference (EFV: r2=0.974, 0.976, 0.972, P<0.001; EFA: r2=0.516, 0.500, 0.477, P<0.001). Threshold adjusting was able to reduce the mean difference, while increase the difference of EFA. Data measured on CCTA and RCCT both demonstrated the significantly larger EFV of Plaque (+) group than Plaque (-) group (P<0.05). The significantly difference of EFA was only shown on RCCT using N30 (Plaque (+) vs (-): -80±4.4HU vs-78±4HU, P=0.030). Conclusion: The consistency of EFV measured on RCCT could be improved through adjustment of attenuation threshold. The EFA assessment may have additional information relating to underlying pathophysiological status.