The clinical application of low dose spiral CT in diagnosis of urinary calcali

Objective:To study the possibility of low-dose spiral CT scanning in the diagnosis of urinary stone.Methods:Seventy-five patients with clinical presentations suspicious for urinary stone were randomly divided into 3 groups:standard-dose group,low dose group 1 and group 2.Standard dose group adopted 120kV,180mA,pitch 0.938:1 for scanning,low-dose group 1 and group 2 used low-dose tube current 120mA and 80mA respectively,and other scanning conditions were the same as the standard dose group.The volume CT dose index(CTDIvol),the dose-length product(DLP) and effective dose(ED) were recorded.Two physicians with more than ten years experience were responsible for making imaging diagnosis and image quality assessment,and calculated the sensitivity,accuracy and positive predicative value in the diagnosis of urinary calculi by standard dose and low dose CT examinations respectively.The subjective quality grading was made of all images and the objective noise value was measured.Results:In the two low-dose groups,as compared with the standard dose group,CT dose index(mGy) was decreased by 29.7% and 55.5%,sensitivity was both 93.8%,accuracy was 96.0% and 95.5% and the positive predictive value was 88.2% and 100%.The differences between the two low-dose groups and the standard dose group were not statistically significant.As to the image quality,although the low-dose scan had increased the noise,all images could meet the diagnostic requirements.Conclusion:Low-dose spiral CT scans can normally diagnose urinary tract stones,greatly reduce the radiation dose for patients.