| Objective To investigate the application value of adaptive statistical iterative reconstruction (ASIR) combined with automatic tube current modulation (ATCM) in the dose reduction of urinary CT scanning. Methods Twenty-five urinary patients underwent spiral CT scanning in routine dose and low dose, respectively, with scanning conditions of tube voltage 120 kV, tube current 10~400 mA, screw pitch 1.375:1, rotation speed 0.5 second per lap, and the ATCM technique was applied. The noise index (NI) in the routine group was 13, and it was 25 in the low-dose group. The imaging construction in the two groups was simultaneously performed with layer thickness of 1.25 mm and five different ASIR weighting coefficients (0, 20%, 40%, 60% and 80%), thus 10 suites of imagings were achieved. The noise values of abdomens aorta at the level of right lobe of the liver and L1 vertebral pedicle and the CT value of renal parenchyma at hilum renalis in these 10 suites of imagings were measured, and their signal noise ratios (SNR) were calculated. The CT dose index volumes (CTDIvol), dose length product (DLP) and effective dose (ED) received in the patients of both groups were recorded, and the imaging quality was independently and blindly evaluated on a five-point scale by two radiologists with more than 5-year diagnositic experiences of epigastric lesions. Statistical analysis was performed with Wilcoxon signed-rank test and comparative t-test. Results In the routine group, the CDTIvol and ED were (8.44±1.97) mGy and (6.13±1.55) mSv, respectively, and in the low-dose group, they were (2.46±0.70) mGy and (1.79±0.54) mSv, with significant differences between the two groups (P<0.05). The mean radiation dose in the low-dose group decreased about 70%, and the imagings obtained from both groups were subjectively scored≥3, all meeting the quality needs of clinical diagnosis. As the ASIR weighting coefficient increased, the noise values of imagings reduced gradually and SNR increased. Conclusion Application of ASIR combined with ATCM in the low-dose urinary CT scanning will significantly decrease the radiation dose to patients, while the acquired medical imagings still could meet the quality needs of clinical diagnosis, and so it is worthy of clinical promotion. |
