The characterization of in vivo urinary phospate stones by spectral CT

To analyze characteristics of urinary phospate stones using spectral CT (rapid kV switching dual-energy CT) in vivo. This study included 55 single-composition and 36 mixed-composition infection stones, which were derived from 38 patients (15 males and 23 females), with median age of 49 years old (range 10–71). The effective nuclear number (Z_eff) peak, its high and low points, average Z_eff value, water- and iodine-based values, and average CT values were detected. Post-surgical infrared spectroscopy results were compared with CT findings. In single-composition stones, 21 were of carbapatite, 20 of struvite, and 14 of brushite. These stones differed significantly in Z_eff peak, its low and high points, average Z_eff value, and iodine-based value. Three compositions had similar water-based and average CT values. The 36 mixed-composition stones all had two Z_eff peaks, which included 23 of carbapatite, 25 of struvite, and 24 of brushite. When 95% confidence intervals of Z_eff peaks in single-composition stones were as standard, this standard 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%). The significance differences were not observed in water/iodine-based, average Z_eff and average CT values. Z_eff peaks in vivo spectral CT revealed some characteristics of various phospate stones.