MRI characteristics of supraclavicular brown adipose tissue in relation to cold‐induced thermogenesis in healthy human adults

Background Brown adipose tissue (BAT) has been proposed as a target to treat obesity and metabolic disease. Currently, 18F‐Fluordeoxyglucose positron emission tomography (FDG‐PET) is the standard for BAT‐imaging. MRI might be a promising alternative, as it is not associated with ionizing radiation, offers a high resolution, and allows to discriminate different types of soft tissue. Purpose We sought to evaluate whether supraclavicular BAT (scBAT) volume, fat‐fraction (FF), and relaxation rate (R2*) determined by MRI can predict its metabolic activity, which was assessed by measurement of cold‐induced thermogenesis (CIT). Study Type Prospective cohort study. Subjects Twenty healthy volunteers (9 female, 11 male), aged 18–47 years, with a body mass index (BMI) of 18–30 kg/m2. Field Strength/Sequence Multiecho gradient MRI for water–fat separation was used on a 3T device to measure the FF and T2* of BAT. Assessment Prior to imaging, CIT was determined by measuring the difference in energy expenditure (EE) during warm conditions and after cold exposure. Volume, FF, and R2* of scBAT was assessed and compared with CIT. In 11 participants, two MRI sessions with and without cold exposure were performed and the dynamic changes in FF and R2* assessed. Statistical Tests Linear regression was used to evaluate the relation of MRI measurements and CIT. P‐values below 0.05 were considered significant; data are given as mean ± SD. Results R2* correlated positively with CIT (r = 0.64, R2 = 0.41 P = 0.0041). Volume and FF did not correlate significantly with CIT. After mild cold exposure EE increased significantly (P = 0.0002), with a mean CIT of 147 kcal/day. The mean volume of scBAT was 72.4 ± 38.4 ml, mean FF was 74.3 ± 5.8%, and the mean R2* (1/T2*) was 33.5 ± 12.7 s‐1. Data Conclusion R2* of human scBAT can be used to estimate CIT. FF of scBAT was not associated with CIT. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1160–1168.