能谱CT去金属伪影技术减低脊柱不同类型植入物伪影的体模研究  

The experimental phantom study of spectral CT metal artifact reduction technique in reducing the artifacts of different types of spinal implants

作　　者：李杰[1] 孙兴文 欧阳汉强 姜亮[2] 袁慧书[1] Li Jie;Sun Xingwen;Ouyang Hanqiang;Jiang Liang;Yuan Huishu(Department of Radiology,Peking University Third Hospital,Beijing 100191,China;Department of Orthopaedics,Peking University Third Hospital,Beijing 100191,China)

机构地区：[1]北京大学第三医院放射科,100191 [2]北京大学第三医院骨科,100191

出　　处：《中华放射学杂志》2021年第9期910-916,共7页Chinese Journal of Radiology

基　　金：北京市自然科学基金(7204327);首都卫生发展科研专项(2020-4-40916)。

摘　　要：目的利用体模评价能谱CT去金属伪影(MAR)技术减低脊柱不同植入物伪影的效果。方法选取离体的羊椎体骨模型1具,分别构建椎弓根钉、3D椎体及钛网内固定模型,行能谱CT检查。以10 keV为间隔,重建出70~140 keV之间共8组MAR和非MAR图像。测量置入物旁ROI内的CT值和SD值,计算伪影指数(AI)和信噪比(SNR),同时对骨质、椎弓根钉伪影、3D椎体伪影及钛网伪影严重程度进行主观评分。绘制AI和SNR随keV变化的曲线,采用配对样本t检验比较低能级(70 keV)、中等能级(100 keV)和高能级(130 keV)条件下MAR和非MAR图像AI值和SNR的差异,主观评分的差异比较采用Wilcoxon符号秩和检验。结果在70~140 keV范围内,MAR和非MAR图像椎弓根钉的前方、后方、侧方和3D椎体以及钛网旁AI值随keV的增加而减低,SNR值改善。在70、100、130 keV条件下,椎弓根钉前方、后方、侧方及钛网旁的AI值在MAR组非较MAR组均明显减低(P<0.05)。3D椎体后方,仅在70 keV条件下,MAR图像AI值较非MAR组减低,差异有统计学意义(P<0.001)。在椎弓根钉前方、后方及3D椎体侧方SNR值随keV增加而增加,在其他部位SNR值随keV增加而减低。主观评价中,MAR图像评分均高于非MAR图像(P<0.05)。结论能谱CT MAR技术能够减低脊柱植入物伪影,可明显减少椎弓根钉及钛网伪影,而对3D椎体后方的减少伪影的效果有限。Objective To evaluate spectral CT metal artifacts reduction(MAR)technique in reducing metal artifacts of spinal implants in a phantom.Methods Ovine spines were chosen as anthropomorphic phantom.The phantom including the pedicle screws,3D-printed vertebral body(VB)and mesh cage were examined using spectral CT.Postoperative CT images were reconstructed at 70—140 keV with 10 keV interval of MAR and non-MAR.Artifact index(AI)and signal-to-noise ratio(SNR)were evaluated by CT and SD values in ROIs around the implants.Visibility of bony structures,the artifacts of pedicle screw,3D-printed VB and mesh cage were subjectively evaluated.Plotting curves of AI and SNR with the increasing keV were drawn.The AI and SNR were compared at lower(70 keV),medium(100 keV)and high(130 keV)level between MAR and non-MAR images using the paired t-test,and the subjective scores were compared using Wilcoxon signed rank-sum test.Results The AI values around pedicle screws(anterior,posterior and lateral),3D-printed VB and mesh cage decreased with the increase of keV,while SNR improved in MAR and non-MAR images.The AI values in the anterior,lateral and posterior pedicle screws and lateral titanium implants were significantly lower in MAR than those in non-MAR(P<0.05).The AI value in posterior 3D-printed vertebral was lower in MAR than that of non-MAR only at 70 keV(P<0.001).The SNR values in the anterior and posterior pedicle screws,3D-printed VB increased with the increase of keV,but decreased in other ROIs.In the subjective evaluation,the image scores of MAR were higher than those of non-MAR(P<0.05).Conclusion Spectral CT using the MAR reconstruction can effectively reduce metal artifacts of spinal implants.The effect is better in pedicle screw and mesh cage than 3D-printed VB.

关 键 词：体层摄影术 X线计算机 单能量成像 金属伪影 脊柱植入物 

分 类 号：R687.3[医药卫生—骨科学]