Determination of Gallstone Composition using Dual-Energy Computed Tomography: An Ex-vivo Study

Abstract

Purpose: This study aimed to investigate whether <i>ex-vivo</i> gallstones are distinguishable by type using dualenergy computed tomography (DECT).Materials and Methods: A total of 124 gallstones from 65 patients with acute or chronic calculous cholecystitis were evaluated using DECT. The extracted gallstones were submerged in distilled water in an acrylic container and scanned at tube voltages of 80/140 kVp and 100/140 kVp. The images were grouped into three sets: 80, 100, and 140 kVp. Qualitative analyses of DECT sensitivity and attenuation patterns in each image set were performed, and quantitative analyses included calculation of mean attenuation values and measurement of the gallstone size. Semi-quantitative Fourier transform infrared (FTIR) spectroscopy was used as the reference standard to confirm the chemical composition of the gallstones.Results: FTIR spectroscopy identified 66 gallstones from 33 patients as cholesterol gallstones and 58 gallstones from 32 patients as pigment gallstones. Qualitative analysis indicated that DECT sensitivity for cholesterol gallstones was greatest at 80 kVp. Most cholesterol gallstones (79%) showed low attenuation at 80 kVp and high attenuation (65%) at 140 kVp. Pigment gallstones demonstrated high attenuation at all image sets. On quantitative analysis, the mean calculated attenuation values of cholesterol gallstones were -17 ± 50 Hounsfield Units (HU), -5.1 ± 43 HU, and 19.2 ± 39 HU at 80, 100, and 140 kVp, respectively, and 342 ± 173 HU, 286 ± 116 HU, and 195 ± 91 HU, respectively, for pigment stones.Conclusions: <i>Ex-vivo</i> gallstones were distinguishable as cholesterol or pigment gallstones by using DECT.