title: Quantification of absolute fat mass using an adipose tissue reference signal model.
abstract: OBJECTIVE
  To develop a method for quantifying absolute fat mass, and to demonstrate its feasibility in phantoms and in ex vivo swine specimens at 3 Tesla.
  
  
  METHODS
  Chemical-shift-based fat-water decomposition was used to first reconstruct fat-only images. Our proposed model used a reference signal from fat in pure adipose tissue to calibrate and normalize the fat signal intensities from the fat-only images. Fat mass was subsequently computed on a voxel-by-voxel basis and summed across each sample. Feasibility of the model was tested in six ex vivo swine samples containing varying mixtures of fat (adipose) and lean tissues. The samples were imaged using 1.5-mm isotropic voxels and a single-channel birdcage head coil at 3 Tesla. Lipid assay was independently performed to determine fat mass, and served as the comparison standard.
  
  
  RESULTS
  Absolute fat mass values (in grams) derived by our proposed model were in excellent agreement with lipid assay results, with a 5% to 7% difference (r > 0.99; P < 0.001).
  
  
  CONCLUSIONS
  Preliminary results in ex vivo swine samples demonstrated the feasibility of computing absolute fat mass as a quantitative endpoint using chemical-shift fat-water MRI with a signal model based on reference fat from pure adipose tissue.
authors.affiliation: Magnetic Resonance Engineering Laboratory, Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089-2564, USA. houchunh@usc.edu
authors.forename: Houchun H
authors.initials: HH
authors.lastname: Hu
authors.forename: Krishna S
authors.initials: KS
authors.lastname: Nayak
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000818:Animals; D005240:Feasibility Studies; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D013552:Swine