双能量能谱CT衰减值鉴别尿酸与非尿酸泌尿系结石的价值

Dual-energy spectrum CT attenuation values for identifying uric acid and non-uric acid urinary calculi

目的探讨能谱CT衰减值区分尿酸和非尿酸泌尿系结石的效能。方法回顾性分析40例症状性尿路结石患者的临床资料(男性26例,女性14例,平均年龄54岁),患者行双源双能CT扫描,采用红外光谱分析结石组成。从双能量数据获取图像域虚拟单能图像,在40~190keV单能图像上评估结石衰减值,得到衰减曲线并计算40/190keV衰减比,最后对能谱衰减曲线行定性评估。结果40例患者共69枚结石(平均直径6.6mm),15枚主要由尿酸和54枚主要由半胱氨酸或草酸钙/磷酸盐组成。尿酸结石40/190 keV的衰减比(0.82±0.28)明显低于非尿酸结石(3.69±0.55,t=-3.982,P<0.001)。40/190keV衰减率阈值取1.69,区分尿酸和非尿酸结石准确度为100%。能谱衰减曲线定性分析可显示尿酸和非尿酸结石的独特形状曲线。结论能谱CT可定量和定性的区分尿酸和非尿酸结石。

Objective To differentiate uric acid from non-uric acid urinary calculi using energy spectrum CT attenuation values.Methods We retrospectively analyzed the clinical data of 40 patients(26 males and 14 females,mean age 54 years)with symptomatic urolithiasis who underwent dual-source dual-energy CT scan.Stone composition was assessed by infrared spectroscopy.Image-domain virtual monoenergetic images were acquired from the dual energy data,and attenuation value of stone was evaluated from 40 to 190 keV monoenergetic images.40/190 keV attenuation ratios were also calculated.Qualitative evaluation of the spectrum attenuation curve was performed.Results Forty patients had a total of 69 stones(average diameter 6.6 mm),including 15 uric acid stones and 54 cysteine or calcium oxalate/phosphate.The attenuation ratio of uric acid stones at 40/190 keV(0.82±0.28)was significantly lower than that of non-uric acid stones(3.69±0.55,P<0.001).Accuracy was 100%with a cut-off value of 1.69.Qualitative analysis of the energy spectrum attenuation curve showed unique shape curves for uric acid and non-uric acid stones.Conclusion Energy spectrum CT could quantitatively and qualitatively distinguish between uric acid and non-uric acid stones.