Magnetic resonance measures of IHL, IMCL, visceral- and subcutaneous- adipose tissue (VAT, SCAT) are conducted on a whole body Siemens 3T Tim
® Trio scanner at the Wolfson Brain Imaging Centre on the Addenbrooke's campus. For IHL, a
1H spectrum is obtained from a voxel of cube length 1.5 cm, located within the posterior aspect of the right lobe of the liver, using the point resolved selective spectroscopy (PRESS) sequence. During this measurement, participants are given breathing instructions with a 7-second cycle, which is designed and gated such that localisation and subsequent data acquisition occur at the end of expiration. Non-water suppressed data are acquired with repetition time (TR) = 7 s, echo time (TE) = 35 ms and averaged over 64 measures. The voxel is positioned to avoid blood vessels and the biliary tree, using T
2-weighted HASTE transaxial images that are also acquired in the same phase of respiration. The voxel is placed in the same location at the participant's follow-up visit. For IMCL measures, localisation images are acquired in three orthogonal directions through the right lower leg. To aid voxel relocation at the follow-up visit and to ensure the transaxial slices are acquired through the largest bulk of the soleus muscle, the localisation images are planned such that the top of the medial femoral condyle is located in the uppermost slice. The voxel (cube length 1.3 cm) is located within the transaxial slice that contains the most homogenous soleus muscle bulk, avoiding fascial lines and visible fat tissue. A water-suppressed spectrum is obtained using the PRESS sequence with TR = 5 s, TE = 35 ms and 64 averages. All spectra are analysed jMRUI [
51] and fitted using the AMARES [
52] algorithm with prior knowledge. IHL and IMCL are quantified relative to water and creatine, respectively. Magnetic resonance imaging (MRI) is then used to measure abdominal fat depots in a transverse section. The L4 vertebral body is placed at the isocentre of a 17-slice, T
1-weighted image with turbo spin echo and water suppression. Transaxial slice thickness is 10 mm with a 2-mm gap. Imaging parameters used are a field of view of 500 × 500 mm, in-plane resolution of 1.3 × 1.3 mm, TR = 400 ms, TE = 21 ms and two averages. Cross-sectional volumes of VAT and SCAT are calculated using a semi-automated method, incorporating a software-generated threshold map (Analyze 7.0, BIR, Mayo Clinic, Rochester MN) which is used in combination with manual input to distinguish the two fat compartments.