64层螺旋CT检测泌尿系结石低kV扫描的优化选择及临床应用

Optimization and application of low-Kilovoltage 64-slice spiral CT scanning parameters in the detection of urinary calculus

目的:探讨64层螺旋CT检测泌尿系结石低kV扫描方案的优化及临床应用。方法:132例泌尿系结石患者随机分成6组(每组22名患者):Ⅰ组(80kV～200mAs组)、Ⅱ组(80kV～300mAs组)、Ⅲ组(100kV～100mAs组)、Ⅳ组(100kV～150mAs组)、Ⅴ组(100kV～200mAs组)、Ⅵ组(120kV～200mAs组)。Ⅵ组为对照组。扫描层厚5mm,层间距5mm,螺距0.984;扫描结束后将获得的扫描原始数据(5mm图像)重建成1.25mm图像。测量5mm图像和1.25mm图像的肾实质的CT值及SD值,计算信噪比(SNR),测量1.25mm层厚图像结石的最大CT值及最大横径,计数结石检出数,对图像进行主观评分并统计优、良、合格及不合格图像的例数。记录各组的辐射剂量指标CTDIvol。结果:测量5mm层厚图像,Ⅲ组的SD值为18.20,Ⅰ组的SD值为17.84,其扫描图像主观评分均合格(>6分),X线辐射剂量比对照组降低了69.01%。5mm图像重建成1.25mm图像后,图像噪声显著增大,与对照组相比,Ⅴ组的噪声增加率仅为28.60%,信噪比降低率仅为11.11%,X线辐射剂量降低了38.02%,其他各实验组与对照组相比噪声增加率均超过了35%。结论:在降低X线照射剂量的情况下,腹部低kVCT扫描(100kV～100mAs,80kV～200mAs)图像质量符合诊断要求,可以作为检查泌尿系结石MSCT扫描的优化条件。

Objective：To investigate the optimization and application of low-kilovoltage 64-slice spiral CT scanning parameters in the detection of urinary calculus.Methods：132 patients with urinary calculus were randomly divided into six groups （22 cases each） with different scanning parameters：GroupⅠ （80kV,200mAs）,GroupⅡ（80kV,300mAs）,GroupⅢ （100kV,100mAs）,Group Ⅳ（100kV,150mAs）,Group Ⅴ （100kV^200mAs）,Group Ⅵ （120kV^200mAs）.Group Ⅵ was set to be the control group.Section thickness：5mm;section interval：5mm;The raw data were reconstructed into 1.25mm.All the raw and reconstructed images were transferred to GE ADW4.3 workstation.The CT attenuation values and standard deviation （SD） of renal parenchyma were measured in the 5mm and 1.25mm images,signal to noise ratios （SNR） were calculated.The images were classified into four grades （excellent,good,qualified,unqualified）.CT dose index volumes （CTDIvol） were obtained automatically.Results：5mm images were measured.SD of Group Ⅲ was 18.2,and SD of GroupⅠwas 17.84.These images were classified into qualified.The CTDIvol of GroupⅢ and GroupⅠwere lower than that of Group Ⅵ by 69.01%.5mm raw images were reconstructed into 1.25mm.The image noise of 1.25mm images was higher accordingly.Compared with the control group,the SNR and the CTDIvol of GroupⅤ were decreased by 11.11% and 38.02%,respectively,and the image noise of GroupⅤ was raised to 128.60%.The image noise of GroupⅠ~Ⅳ was significantly increased by over 35%.Conclusion：For decreasing the radiation dose,100kV^100mAs and 80kV^200mAs were the optimal protocols of low-kilovoltage CT scanning for detection of urinary calculus.