The characterization of in-vivo urinary infection stones by spectral CT

Abstract Purpose To analyze characteristics of urinary infection stones using spectral CT (rapid kV switching dual-energy CT) in vivo. Methods This study included 55 single-composition and 36 mixed-composition infection stones, derived from 38 patients (15 males and 23 females), median age 49 (range, 10–71) years. We detected and compared effective nuclear number (Zeff) peak, its high and low points, average Zeff value, water- and iodine-based values, and average CT values. Post-surgical infrared spectroscopy results were compared with CT findings. Results In single-composition stones, 21 were of carbapatite, 20 of struvite, and 14 of brushite. These differed significantly in Zeff peak, its low and high points, average Zeff value, and iodine-based value. Three compositions had similar water-based and average CT values. The mixed-composition stones all had two Zeff peaks, and Zeff peaks in 36 mixed-composition stones included 23 of carbapatite, 25 of struvite, and 24 of brushite. When 95% confidence intervals of Zeff peaks in single-composition stones were as standard, they overlapped 82.6% of carbapatite, 88.0% of struvite, and 87.5% of brushite in mixed-composition stones. But many low and high points in three mixed-composition groups were outside the 95% confidence interval (overlap < 70%). Differences in water/iodine-based, average Zeff and average CT values did not reach the significance level. Conclusion Zeff peaks of urinary infection stones in vivo spectral CT revealed characteristics of various infective compositions.