In vitro dissolution of gallstones with MTBE: correlation with characteristics at CT and MR imaging

The authors undertook a study to determine whether in vitro computed tomography (CT) or magnetic resonance (MR) imaging could enable the prediction of the outcome of gallstone dissolution with methyl tert-butyl ether (MTBE). In vitro CT and MR images were obtained of gallstones removed at surgery from 40 and 30 patients, respectively. The patterns of the gallstones seen on CT scans were categorized as dense, moderately dense, faint, isodense, rimmed, and laminated. Gallstones were categorized by maximal signal intensities seen on T1-weighted MR images. After imaging, gallstones underwent in vitro MTBE dissolution. CT appearances correlated well with dissolution rates. Greatest weight change was noted in gallstones with homogeneously faint and isodense patterns, and least weight change was seen in stones with a homogeneously dense pattern. Rimmed and laminated stones with foci of high attenuation dissolved significantly to 5% or less of the original weight, a finding indicating that such foci do not preclude dissolution. Dissolution rates correlated with attenuation values of homogeneous stones (r = .8) and of the rim portion of rimmed stones (r = .8). No correlation was found between T1-weighted signal intensities on MR images and MTBE dissolution rates.