Department of Radiology, Faculty of Medicine and Health, Örebro University, 701 85, Örebro, Sweden.
Urolithiasis. 2018 Aug;46(4):325-332. doi: 10.1007/s00240-017-0994-x. Epub 2017 Jun 28.
Urinary stones composed of uric acid can be treated medically. Prediction of uric acid stone type is, therefore, desirable when a urinary stone is diagnosed with unenhanced CT. The purpose of the present study was to describe single-energy thin slice quantitative CT parameters of urinary stones correlated to chemical stone type and to develop a method to distinguish pure uric acid stones (UA) from other stones (non-UA/Mix). Unenhanced thin slice single-energy CT images of 126 urinary stones (117 patients) with known chemical stone type were retrospectively included in the study. Among the included stones, 22 were UA and 104 were non-UA/Mix. The included CT images and Laplacian filtered images of the stones were quantitatively analyzed using operator-independent methods. A post hoc classification method for pure UA stones was created using a combination of cutoff values for the peak attenuation and peak point Laplacian. The stone types differed in most quantitative image characteristics including mean attenuation (p < 0.001), peak attenuation (p < 0.001), and peak point Laplacian (p < 0.001). The sensitivity for the post hoc-developed peak attenuation-peak point Laplacian method for classifying pure UA stones was 95% [21/22, 95% CI (77-100%)] and the specificity was 99% [103/104, 95% CI (95-100%)]. In conclusion, quantitative image analysis of thin slice routine single-energy CT images is promising for predicting pure UA content in urinary stones, with results comparable to double energy methods.
尿酸结石可以通过医学方法进行治疗。因此，当诊断出尿路结石时，期望能预测尿酸结石的类型。本研究的目的是描述与化学结石类型相关的尿路结石的单能量薄层定量 CT 参数，并开发一种区分纯尿酸结石（UA）与其他结石（非-UA/Mix）的方法。本研究回顾性纳入了 117 例 126 例已知化学结石类型的尿路结石患者的未增强薄层单能 CT 图像。在纳入的结石中，22 例为 UA，104 例为非-UA/Mix。使用独立于操作者的方法对纳入的结石 CT 图像和拉普拉斯滤波图像进行定量分析。使用峰衰减和峰点拉普拉斯的组合的截止值，创建了用于纯 UA 结石的事后分类方法。大多数定量图像特征（包括平均衰减（p < 0.001）、峰值衰减（p < 0.001）和峰点拉普拉斯（p < 0.001））显示结石类型不同。用于分类纯 UA 结石的事后开发的峰衰减-峰点拉普拉斯方法的灵敏度为 95%[21/22，95%CI（77-100%）]，特异性为 99%[103/104，95%CI（95-100%）]。总之，薄层常规单能 CT 图像的定量图像分析有望预测尿路结石中的纯 UA 含量，其结果可与双能方法相媲美。
