自适应统计迭代重组技术对儿童胸部CT辐射剂量和图像质量的影响

Impact of adaptive statistical iterative reconstruction-V on radiation dose and image quality in children with chest CT scan

目的探讨自适应统计迭代重组(adaptive statistical iterative reconstruction Veo, ASIR-V)技术在儿童胸部平扫中降低辐射剂量和提高图像质量的价值。方法采用GE Revolution-CT对280例儿童胸部平扫患者进行扫描。280例患者随机分成4组,每组70例;对照组设为A组,前置ASIR-V权重设置为0,实验组设为B-D组,前置ASIR-V权重分别设置为70%、80%和90%。记录各组患者扫描的剂量长度乘积(DLP),计算并比较各组有效剂量(ED)。图像客观评价在CT轴位图像上选取气管隆突层面测量各重组图像皮下脂肪、竖脊肌的CT值和标准差SD值,同时以背部竖脊肌为参考计算皮下脂肪、竖脊肌的信噪比(SNR)。采用5分法对图像进行主观评分。采用统计学方法比较各组的辐射剂量、客观图像质量并比较两组图像的主观质量评分。结果平均ED值为:A组1.3±0.22 mSv,B组0.68±0.06 mSv,C组0.37±0.38 mSv,D组0.15±0.03 mSv。图像质量评价方面,在肺窗及纵隔窗上,70%ASIR-V图像具有较好的图像质量,各ROI的SD值(12.09±3.44,12.37±3.58)明显低于0%及80%、90%ASIR-V图像的相应SD值(P<0.05),SNR (4.83±0.62,2.93±0.54)明显高于0%及80%、90%ASIR-V图像的相应SNR值(P<0.05);同时,70%ASIR-V图像在肺窗及纵隔窗的主观评分(4.15±0.51,4.09±0.53)亦优于0%及80%、90%ASIR-V图像的评分值(P<0.05)。结论前置ASIR-V权重为70%不仅保证临床诊断需求,且辐射剂量明显降低。

Objective To investigate the impact of adaptive statistical iterative reconstruction-V(ASIR-V)on radiation dose and image quality in children with chest CT scan.Methods 280 patients underwent chest CT scan using a 256-row multi-detector CT(MDCT).The patients are divided into 4 groups(A,B,C and D)of 70 each.Conventional FBP reconstruction algorithm was used in group A.The dose length product(DLP)of each patient's scan was recorded,and the effective dose(ED)of each group was calculated and compared.The CT and SD values of subcutaneous fat and erector spinae were measured at the tracheal carina level,and the signal-to-noise ratio(SNR)of subcutaneous fat and erector spinae was calculated using the dorsal erector spinae as a reference.Subjective image quality was assessed independently by three radiologists.A five-point scale(from 1=poor to 5=excellent)system was used.The Mann-Whitney U test and Kruskal-Wallis H test was used to test whether measurements between groups were different.Results Radiation dose in the study group was reduced as compared with the control group.Effective dose in group B(0.68±0.38),C(0.37±0.06),and D(0.15±0.03)were lower than group A(1.3±0.22).On the image quality evaluation,70%ASIR-V image has better image quality on the lung window and the mediastinum window.The SD value of fat and muscle(12.09±3.44,12.37±3.58)is obviously lower than the SD value of 0%,80%and 90%ASIR-V(P<0.05),The SNR(4.83±0.62,2.93±0.54)was significantly higher than the SNR value(P<0.05)of the 0%,80%and 90%ASIR-V images,and the subjective score of the 70%ASIR-V image in the lung and medial window(4.15±0.51,4.09±0.53)was also better than the score of 0%,80%and 90%ASIR-V(P<0.05).Conclusion The ASIR-V technique of GE Revolution-CT with 70%pre-ASIR-V can reduce radiation dose while maintain good overall image quality.