Study of Conventional Quantitative CT in the Identification of Urinary Tract Stones

Objective: The aim of this study is to assess the value of spiral CT parameters in differenting stone composition of urinary tract. Methods: Preoperative CT data of 112 patients with urinary calculi in our hospital from May 2016 to March 2018 were collected. All images were reviewed using abdomen windows to evaluate the following data of stone: the diameter (d), mean CT value (HUm), standard deviation of the mean CT value (HUsd), and the ratio of average CT value/diameter (HUd). The the differences of various stone components were compared for the above factors with statistical methods. Diagnostic performance of the d, Hum, HUsd and HUd for different stone components were measured by receiver operating characteristic curve (ROC curve). Results: There were 21 cases of uric acid stones, 49 cases of calcium oxalate monohydrate, 10 cases of carbonate apatite and 27 cases of mixed stones. The HUm, HUsd and HUd values of uric acid stones were significantly lower than other types of stones, and the difference were statistically significant between uric acid stones and non-uric acid stones (n calcium oxalate stone, carbonate apatite and mixed stones) in HUm, HUsd and HUd values (P<0.05). There were no significant difference in HUm, HUsd and HUd values between non-uric stones (P>0.05). There was no significant difference in the d value of various stones (P>0.05). The area under the ROC curve of d, HUm, HUsd and HUd to identify the stone components were 0.444, 0.915, 0.972 and 0.858, respectively. Conclusion: The HUm, HUsd and HUd values of spiral CT can identify uric acid stones and non-uric acid stones. Among them, HUsd has the best identification efficiency, but it cannot distinguish all types of non-uric acid stones.