Voxel-wise Study of Cohort Associations in Whole-Body MRI: Application in Metabolic Syndrome and Its Components.

Background The metabolic syndrome is related to obesity and ectopic fat distribution. Purpose To investigate whether an image analysis approach that uses image registration for whole-body voxel-wise analysis could provide additional information about the relationship between metabolic syndrome and body composition compared with traditional image analysis. Materials and Methods Whole-body quantitative water-fat MRI was performed in a population-based prospective study on obesity, energy, and metabolism between October 2010 and November 2016. Fat mass was measured with dual-energy x-ray absorptiometry (DXA). Whole-body voxel-wise analysis of tissue volume and fat content was applied in more than 2 million voxels from the whole-body examinations by automated interindividual deformable image registration of the water and fat MRI data. Metabolic syndrome was diagnosed by the harmonized National Cholesterol Education Program criteria. Two-tailed t tests were used and P values less than .05 were considered to indicate statistical significance. Results This study evaluated 167 women and 159 men (mean age, 50 years) by using voxel-wise analysis. Metabolic syndrome (13.5%; 44 of 326) was related to traditional measurements of fat distribution, such as total fat mass at DXA, visceral and subcutaneous adipose tissue, and liver and pancreatic fat at MRI. Voxel-wise analysis found metabolic syndrome related to liver, heart, and perirenal fat volume; fat content in subcutaneous fat in the hip region in both sexes; fatty infiltration of leg muscles in men, especially in gluteus maximus; and pericardial and aortic perivascular fat mainly in women. Sex differences in associations with subcutaneous adipose tissue were identified. In women, metabolic syndrome diagnosis was linked to regional differences in associations to adipose tissue volumes in upper versus lower body, and dorsal versus ventral abdominal depots. In men similar gradients were only seen in individual components. Conclusion In addition to showing the relationships between metabolic syndrome and body composition in a detailed and intuitive fashion in the whole body, the voxel-wise analysis provided additional information compared with traditional image analysis. © RSNA, 2020 Online supplemental material is available for this article.