Quantification of epicardial fat using 3D cine Dixon MRI

Background: There is an increased interest in quantifying and characterizing epicardial fat which has been linked to various cardiovascular diseases such as coronary artery disease and atrial fibrillation. Recently, three-dimensional single-phase Dixon techniques have been used to depict the heart and to quantify the surrounding fat. The purpose of this study was to investigate the merits of a new high-resolution cine 3D Dixon technique for quantification of epicardial adipose tissue and compare it to single-phase 3D Dixon in patients with cardiovascular disease. Methods: Fifteen patients referred for clinical CMR examination of known or suspected heart disease were scanned on a 1.5T scanner using single-phase Dixon and cine Dixon. Epicardial fat was segmented by three readers and intra- and inter-observer variability was calculated per slice. Cine Dixon segmentation was performed in the same cardiac phase as single-phase Dixon. Subjective image quality assessment of water and fat images were performed by three readers using a 4-point Likert scale (1=severe; 2=significant; 3=mild; 4=no blurring of cardiac structures). Results: Intra-observer variability was excellent for cine Dixon images (ICC=0.96), and higher than single-phase Dixon (ICC=0.92). Inter-observer variability was good for cine Dixon (ICC=0.76) and moderate for single-phase Dixon (ICC=0.63). The intra-observer measurement error (mean ± standard deviation) per slice for cine was -0.02±0.51 ml (-0.08±0.4%), and for single-phase 0.39±0.72 ml (0.18±0.41%). Inter-observer measurement error for cine was 0.46±0.98 ml (0.11±0.46%) and for single-phase 0.42±1.53 ml (0.17±0.47%). Visual scoring of the water image yielded median of 2 (interquartile range = [Q3-Q1] 2-2) for cine and median of 3 (interquartile range = 3-2) for single-phase ( P < 0.05) while no significant difference was found for the fat images, both techniques yielding a median of 3 and interquartile range of 3-2. Conclusion: Cine Dixon can be used to quantify epicardial fat with lower intra- and inter-observer variability compared to standard single-phase Dixon. The time-resolved information provided by the cine acquisition appears to support the delineation of the epicardial adipose tissue depot.