Use of proton MR spectroscopy and MR imaging to assess obesity

We used H-1 MR spectroscopy and MR imaging at 9,4-T to quantify and localize fat and water in the abdominal regions of 12 lean, normal, and obese mice, The D2O dilution method which measures also the equilibrium plasma D2O concentration by H-2 MR spectroscopy was used to quantify body water and fat, In obese mice, the intensity of the fat H-1 resonance was about 120% that of the water 1H resonance, about threefold higher than its value (about 45%) in normal mice. In lean mice, the fat/water intensity ratio was about 1:4, about half that in normal mice. Total body water was similar in obese and normal mice (19.9 +/- 1.5 and 18.7 +/- 1.3 mt) despite their very different body weights (50.1 +/- 3.1 g and 30.2 +/- 3.1 g, respectively), but slightly lower in lean mice (14.8 +/- 1.2 mt water; 22.1 g +/- 2.0 g weight), Selective methylene-proton images showed marked accumulation of fat in the abdomen and the retroperitoneal and subcutaneous spaces of obese mice. Selective water-proton images allowed clear resolution of the renal cortex, medulla, papilla, and urinary pelvis. The readily measurable resonance intensity ratio of abdominal fat to water is a sensitive index by which to characterize obesity.