Résumé
PURPOSE: To evaluate the utility of signal intensity differences between in- and opposed-phase MRI and the lipid peak ratio in in-vivo proton MR spectroscopy of the gallbladder as diagnostic tools for measuring the lipid content of gallbladder bile. MATERIALS AND METHODS: Twenty-six normal volunteers underwent MR imaging (FMPSPGR) and in-vivo proton MR spectroscopy of the gallbladder. In all cases the results of liver function tests were normal, as were cholesterol levels, and ultrasonography of the gaubladder revealed nothing unusual. For MRI and MRS a 1.5T unit (Signa Horizon; GE Medical Systems, Milwaukee, U.S.A.) was used. In-phase and opposed-phase coronal-section MR images(FMPSPGR; TR=125 msec, TE=1.8, 4.2 msec) of the gallbladder were obtained, and differences in signal intensity thus determined. For proton MR spectroscopy of the gallbladder, a localized proton STEAM sequence was employed. A single voxel of 1-8 cm3 was placed at the center of the gallbladder cavity, peak areas at 0.8-1.6 ppm (lipid), 2.0-2.4 ppm, 3.2-3.4 ppm, 3.9-4.1 ppm, and 5.2-5.4 ppm were measured by proton MRS and the relative peak area ratios of peak 0.8-1.6 ppm/other peaks were calculated. The degree of correlation between signal intensity differences at MRI and the relative peak area ratio of lipid in proton MRS was estimated using the p-value and Pearson's correlation coefficient. RESULTS: Signal intensity differences ranged from 11.3 to 43.4% (mean, 26+/-8.9%), and the range of lipid peak area ratio at MRS was 0.10-0.97 (mean, 0.66+/-0.21). There was significant correlation between the two measured values (p=0.014, Pearson's correlation coefficient=0.478). CONCLUSION: In normal cystic bile, signal intensity differences at in- and opposed-phase MRI and relative lipid peak area ratios at MRS varied, though both methods could be used diagnostically for measuring the lipid contents of body tissue.