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

摘要

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％.%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.