The Application Value In The Diagnosis Of The Urinary Calculi By Low-dose CT Scanning Technique Combined With The Iterative Reconstruction In Image Space

Objective: To discuss the application value in the diagnosis of the urinary calculi by low-dose CT scanning technique combined with the iterative reconstruction in image space.Methods: This study is divided into two parts, the first part is phantom scanning, and the second part is the clinical study.The first part: Six common kinds of vitro urinary calculi were collected in clinical from urology: calcium oxalate stones, uric acid stones, calcium phosphate stones, magnesium ammonium phosphate stones, cystine stones, calcium oxalate and calcium phosphate stones mixed. Those urinary calculi were implanted into six pig kidneys, two for each kidney; 5mm and 2mm diameter of the same kind of stone were implanted into each kidney respectively. The kidney were scanned in a cylinder-shaped glass container, which is filled with 0.9% Na Cl solution, while the scanning tube voltage is 130 k V, decreased the tube current gradually, m As was 250, 200, 150, 100, 50, 30 respectively. There are two doctors reading different m As scanning image above, to analyze the size and location of each kidney stone.The second part: 50 cases of suspected urinary calculi diseases were studied. The patients were scanned by normal dose and low dose, low-dose scan conditions were carried out by the above phantom experiment. Image reconstruction was performed by using the methods of FBP(Filtered Back-projection) and IRIS(Iterative Reconstruction in Image Space) with the data got from the low-dose scan. The CTDIvol(CT dosed index volume) was used to calculate the lower doses of radiation Recorded After the scan for each patient, SD and the SNR were perform as the image quality objective criteria. Three physicians review on the images of conventional dose group, low-dose FBP group and low-dose IRIS group, including location, size of urinary stone, the size of the kidney, hydronephrosis, and trabs of perirenal fat.Statistical analysis was performed by SPSS 17.0 software, the detection rate of stone for conventional-dose group, low-dose group used Fisher exact test. The test of normality was made on CTDIvol of the normal dose and low dose, the image noise, and the change of SNR of the two kinds of reconstruction using the method of paired-sample t test; Difference was statistically significant(P < 0.05).Results:1 Twelve kidney stones(calcium oxalate stones, uric acid calculi, calcium phosphate, magnesium ammonium phosphate stones, cystine, calcium oxalate and calcium phosphate mixed stones, 2 stones of each kind) could be checked out, when the tube voltage was 130 k V, and the m As was gradually reduced to 250, 200, 150, 100, 50 and 30. The detection rate was 100%.2 Seventy-two stones of 38 patients were detected in conventional-dose group, 1 mm ~ 25 mm diameter size, 69 from the low-dose FBP group and low-dose FBP group, detection rate is about 95.8%, 3 kidney stones of 1mm-diameter were not detected. There no statistically significant difference between the conventional-dose group and low-dose group(P=0.245). Standard conventional dose group, low-dose scanning’s sensitivity and specificity for the diagnosis of stones was 95.8% and 100% respectively.3 For the 38 cases of urinary calculi, 23 cases of hydronephrosis, 7 cases of trabs of perirenal fat and 10 cases of kidney increases were found in the conventional-dose group. And 23 cases of hydronephrosis, 7 cases of trabs of perirenal fat and 10 cases of kidney increases were found in Low-dose FBP group of 30 m As. 23 cases of hydronephrosis, 7 cases of trabs of perirenal fat and 10 cases of kidney increases were found in Low-dose IRIS group of 30 m As.4 The average CTDIvol was 18.60±3.63m Gy in the normal dose group,and 2.82±0.30m Gy from the low dose group,reduced by 85%,There was statistically significant difference between the two group(t=32.396,P=CT计算机体层摄影Computed tomography IRIS图像域迭代重建算法Iterative Reconstruction in Image Space IR迭代重建Iterative Reconstruction FBP滤波反投影算法Filtered Back-projection KUB腹平片Plain Film of Kidney,Ureter,and Bladder IVP静脉肾盂造影Intravenous Pyelography US超声Ultrasound MR磁共振Magnetic Resonance CTU CT摄影尿路成像CT Urography MRU MR尿路成像MR Urography CTDIvol CT容积剂量指数CT Dose Index Volume SD标准差Standard Deviation SNR信噪比Signal to Noise Ratio BMI体重指数Body Mass Index 0.000).5 compared with FBP, The image average noise of IRIS(13.560±0.379) was lower than that of FBP(21.280±0.612),the difference between them was statistically significant(t=-14.166,P=0.000). The average SNR(2.052±0.076) was higher than that of FBP(1.307±0.052), the difference between them was statistically significant(t=14.166, P=0.000).Conclusion:Compared with conventional-dose CT scan by 130 k V, 250 m As, Low-dose CT scan by 130 k V, 30 m As significantly reduce the radiation dose to the patient, and there was no significant difference in the diagnosis of urinary calculi detection rate. There was no difference in the detection rate of stones and stone obstruction secondary display signs between Low-dose IRIS and low-dose FBP group, and the image quality was better than that of the low-dose FBP group. Therefore, low-dose CT scanning technology combines with IRIS worth promoting in the diagnosis of urinary calculi in clinical applications.