In vitro investigation of gallstones with computed tomography.

An in vitro investigation of gallstones from 25 patients using computed tomography (CT) was performed). An abdominal phantom was constructed and filled with a matrix with an attenuation value equivalent to normal liver. A condom filled with water and positioned within the phantom simulated the gallbladder. Gallstones were placed in the condom and were scanned, radiographed, measured, and inspected. All gallstones were detectable by CT as filling defects within the condom having CT attenuation values higher or lower than water. Attenuation values ranged from +178 to -188 CT units (scale, +500 to -500). Gallstones containing calcium settled to the bottom of the condom, while calculi containing gas filled fissures rose to the top of the condom.