不同权重自适应迭代算法重组对儿童腹部CT平扫图像质量的影响

Effects of different adaptive statistical iterative reconstruction-V percentage on pediatric abdominal computed tomography

目的不同权重自适应迭代算法(ASIR-V)重组对儿童低剂量腹部CT平扫图像质量的影响。方法随机选取30例,腹部平扫,扫描范围:膈面至耻骨联合,扫描条件:256排螺旋CT 100 k V,自动毫安,螺旋扫描,螺距0.992,层厚5 mm,噪声指数(noise index,NI):9,ASIR-V:50%,后处理:ASIR-V按10%的间隔,在范围0~100%内重组出11组图像,层厚1.25mm,选取门静脉主干层面、肝脏下缘层面、耻骨联合层面,测量背部肌肉的CT值及标准差(SD)并计算信噪比(SNR)。由20年以上工作经验的两名副主任医师独立评片,图像质量主观评分采用5分制,图像评分标准:1分,图像噪声大,组织间分界不清,不能用于诊断;5分,图像质量非常好,组织间分界清晰,可以满足诊断。记录4分以上图像的ASIR-V权重范围,对两位阅片者阅片的结果一致性采用Weighted Kappa检验。结果两位医师阅片结果一致性良好,ASIR-V为40%~70%的图像均在4分以上。结论儿童低剂量腹部CT平扫技术加以40%~70%的ASIR-V重组得到的图像质量良好,对合理设置儿童腹部CT平扫的迭代权重有重要价值。

Objective To study the influence of different adaptive statistical iterative reconstruction-V(ASIR-V)percentages on quality of low-dose abdominal CT images of children.Methods 30 consecutive children underwent abdominal CT plain scan,scanning range:diaphragm to symphysis pubis.All children were scanned at 9 HU(5 mm slice thickness)noise index levels of automatic current modulation with 100 kV on 256-row CT scanner.Images were reconstructed with different ASIR-V percentage from 0%to 100%at a 10%interval.Selected the level of the main level of the portal vein,the lower edge of the liver,and the symphysis pubis.Measured the CT value and standard deviation(SD)of the back muscles,and calculated signal to noise ratio(SNR).The overall subjective image quality and diagnostic acceptability was assessed using a 5-point scoring system(5 good;1 bad).Weighted Kappa test was used to analyze the image-reviewing consistency of the two reviewers.Results The image-reviewing results of the two physicians showed good consistency.The score was all≥4 points with ASIR-V of 40%-70%percentage.Conclusion Low-dose abdominal scanning technique in children combined with 40%-70%ASIR-V reconstruction can acquire good image quality.Rational setting of the iterative weight of CT plain scan in abdomen of children can be useful and valuable.