多模型迭代重建算法对腹部体模CT扫描图像质量和辐射剂量的影响

目的 分析前置全模型迭代重建算法（ASIR-V）在腹部体模CT扫描中图像质量的变化规律及辐射剂量的降低程度，探讨优化图像质量和辐射剂量的最佳前置ASIR-V。方法 采用腹部仿真体模和Revolution CT机。根据噪声指数（NI）设置（6、8、10、12、14）分为5组。每组设置0~100%（间隔10%）前置ASIR-V扫描和常规扫描（即不联合迭代），共获得55组图像。分析各NI组图像CT值、噪声、主观评分及辐射剂量随ASIR-V比例的变化规律。各NI组图像的主观评分比较采用秩和检验，CT值、噪声和辐射剂量比较采用单因素方差分析和配对t检验。结果 在0~40%前置ASIR-V水平，NI为6、8、10组图像主观评分基本稳定，NI为12、14组图像主观评分呈略升高趋势；50%~100%前置ASIR-V，各组主观评分均呈逐渐降低趋势；NI为6、8、10组，超过70%前置ASIR-V图像主观评分降至3分以下，NI为12、14组，超过60%前置ASIR-V主观评分降至3分以下；NI为6、8、10组，常规扫描图像主观评分与40%前置ASIR-V图像差异无统计学意义（P=0.626、0.915、0.514），NI为12、14组，常规扫描图像主观评分略低于40%前置ASIR-V图像（P=0.041、0.036）；各NI组常规扫描图像主观评分均优于60%前置ASIR-V图像（（P=0.021、0.012、0.015、0.014、0.007））。各NI组中不同部位CT值、噪声随前置ASIR-V比例的增高呈基本稳定状态（P均>0.05）。各NI组CTDIvol随前置ASIR-V比例的增高，呈逐渐下降趋势。40%、50%和60%前置ASIR-V比例条件下，CTDIvol较常规扫描组下降比率分别为49.82%、62.51%、71.63%。结论 前置ASIR-V可在保证图像质量的条件下明显降低辐射剂量；腹部前置ASIR-V比例推荐40%~60%。

Influence of adaptive statistical iterative reconstruction-V on image quality and radiation dose of abdominal CT in phantom

Objective To evaluate the influence of preset adaptive statistical iterative reconstruction-V (ASIR-V) techniques on image quality and radiation dose reduction of abdominal CT in phantom, and to investigate the optimal ASIR-V level.Methods Abdominal anthropomorphic phantom was scanned using Revolution CT, when noise index (NI) were set as 6, 8, 10, 12 and 14, respectively. Then 0-100% ASIR-V and conventional scan was performed and 55 sets of images were obtained. CT value, noise, subjective score and radiation dose were recorded, and the optimal ASIR-V was obtained. Subjective scores of images in each group were compared using rank sum test, and CT value, noise and radiation dose were compared with one way ANOVA and paired t test.Results The image subjective score unchanged when NI was 6, 8 or 10, slightly increased when NI was 12 and 14 with 0-40% ASIR-V, and decreased above 50% ASIR-V at all NI. When NI was 6, 8 or 10, more than 70% ASIR-V image subjective score fell below 3 points. When NI was 12 or 14 group, more than 60% ASIR-V subjective score fell below 3 points. The image quality score of conventional scan had no difference with 40% ASIR-V when NI was 6, 8 or 10, respectively (P=0.626, 0.915, 0.514), and inferior to 40% ASIR-V when NI was 12 or 14 (P=0.041, 0.036), while in all NI group, image quality score of conventional scan was superior to 60% ASIR-V (P=0.021, 0.012, 0.015, 0.014, 0.007). CT values and image noises had no significant differences in different parts in all NI groups (all P>0.05). CT dose index volume (CTDIvol) continuing decreased with ASIR-V. Compared with that of conventional scan, at 40%, 50% and 60% ASIR-V, CTDIvol reduced by 49.82%, 62.51% and 71.63%, respectively.Conclusion Preset ASIR-V can reduce radiation dose obviously while maintaining the overall image quality, and 40%-60% ASIR-V can be recommended for abdominal CT in clinical application.