The Analysis Of Urinary Calculi Composition By Low-Dose CT Combined With Iterative Algorithm

Objectives To evaluate the feasibility of analyzing lithangiuria component by using CT low dose combined iterative algorithm,and discuss on the optimal scanning solution.Methods Part 1:60 calculi after urologic surgical procedures were collected,cleaned up by distilled water,dried naturally,numbered,placed inside pig kidney collecting system into groups with recording positions.Then put them fabricated organization model to render CT scanning in different doses.Conventional dose: 120 k V,400 m As,filtered back projection(FBP)1mm thin-slice reconstruction;low dose:(Group A: 120 k V,200 m As;group B: 20 k V,150 m As;group C: 120 k V,100 m As);applied iterative algorithm i Dose1-6 level 1mm thin-slice reconstruction respectively.After the scanning,60 stones were determined by infrared spectrometry,as the gold standard of the experment.Measured calculi soft-tissue window and bone window CT values respectively under conventional dose FBP1 mm reconstruction to preliminarily determine calculi chemical component;two radiographers adopted double-blind method film reading and implemented subjective scoring on image quality,recorded CT CTDIvol,DLP and calculated ED;measured image objective noise value,calculated signal-to-noise ratio,measured calculi CT value and maximum long diameter,recorded calculi detected number,evaluated the influence of low dose combined iterative algorithm on calculi detection and image quality.Part 2: 78 lithangiuria patients were collected;applied conventional dose(120k V/400 m As)scanning to first test and adopted FBP1 mm thin-slice reconstruction;the calculi failed to be eliminated;re-examination CT used low dose(120k V/150 m As)scanning and rendered iterative algorithm i Dose1-6 level 1mm thin-slice reconstruction;firstly,evaluated optimal i Dose level of 1mm through image quality evaluation and calculi detection,and then adopted 1.5mm as well as 2mm reconstruction to this level so as to evaluate the most reasonable reconstruction slice thickness.Results 1 Among the 60 urinary calculi,23 were pure calculi(8 were pure uric acid calculi)and 37 combination calculi;the bone window CT values of 60 calculi were generally higher than soft-tissue window CT values,but the difference was not statistically significant(P >0.05);the difference of CT values between 8 pure uric acid calculi(softtissue window and bone window)and 52 non uric acid calculi(soft-tissue window and bone window)was statistically significant(P <0.05);according to ROC curve,the optimal critical value(CT value)of pure uric acid calculi was determined as 483.5HU;soft-tissue window CT value<483.5HU was taken as standard to diagnose pure uric acid calculi with sensitivity 96.20%,specificity 87.50%.The difference of CTDIvol,DLP and ED between low dose group and conventional group was statistically significant(P<0.05);the difference of i Dose1~6 image calculi detection number and calculi CT values as well as sizes between low does and conventional dose was not statistically significant(P >0.05);the difference of subjective scorings of i Dose4 image noise,signal-to-noise ratio and i Dose4-6 image quality between group A and conventional dose was not statistically significant(P >0.05);the difference of subjective scorings of i Dose6 image noise,signalto-noise ratio and image quality between group B and conventional dose was not statistically significant(P >0.05);the difference of subjective scorings of i Dose1-6 image noise,signal-to-noise ratio and image quality between group C and conventional dose was statistically significant(P<0.05).(2)In clinical research,the difference of CTDIvol,DLP and ED between low dose and conventional dose was statistically significant(P<0.05);the difference of i Dose1~6 image calculi detection number and calculi CT values as well as sizes between low does combined iterative algorithm 1mm reconstruction and conventional dose was not statistically significant(P>0.05);the difference of subjective scorings of image noise,signal-to-noise ratio and image quality between i Dose1-5 1mm reconstruction and conventional dose was statistically significant(P<0.05);the difference of subjective scorings of image noise,signal-to-noise ratio and image quality between i Dose6 1mm reconstruction and conventional dose was statistically significant(P<0.05);the difference of image noise between i Dose6 1.5mm as well as 2mm reconstruction and 1mm was statistically significant(P<0.05);the difference of image signal-to-noise ratio between idose6 1.5mm and 1mm reconstruction was not statistically significant(P>0.05);the difference of image signal-to-noise ratio between idose6 2mm and 1mm reconstruction was statistically significant(P<0.05);the difference of calculi CT value between i Dose6 1.5mm and 1mm reconstruction was statistically significant(P<0.05);i Dose6 2mm reconstruction calculi detection number was lower than that in 1mm and 1.5mm reconstruction;the difference of subjective scorings of slice thickness image quality in three groups was not statistically significant(P>0.05).Conclusions 1 According to the different calculi CT values by conventional CT and conventional dose,it is available to distinguish into pure uric acid calculi and non pure uric acid calculi,pure uric acid calculi CT value less then 483.5HU.2 Under the condition of low dose scanning,the iterative algorithm i Dose can improve the image quality,and it has no effect on the detection of urinary calculi and the accuracy of CT value measurement,can be used to evaluate the composition of urinary stones.3 In order to achieve the image quality level of conventional dose,when tube voltage at 120 k V,150 m As of tube current in i Dose6 level is the minimum critical level,where the 1.5mm slice thickness reconstruction is the most optimal solution for the diagnosis of urinary calculi.