比较CS-SEMAC、HBW和Dixon三种去金属伪影技术在脊柱金属植入术后MRI的应用价值

Comparison of the value of CS-SEMAC,HBW,and dixon techniques for postoperative magnetic resonance imaging of spinal metal implants

目的探讨压缩感知结合层面编码金属伪影校正(compressed sensing-slice-encoding metal artifact correction,CS-SEMAC)技术用于脊柱金属植入物术后MRI的应用价值。材料与方法比较招募的35例脊柱金属植入物术后患者3.0 T MRI矢状位CS-SEMAC序列、高带宽(high bandwidth,HBW)序列和水脂分离(Dixon)三种序列在金属植入物伪影面积、椎体信噪比(signal-to-noise ratio,SNR)、图像质量、图像清晰度、脂肪抑制效果以及植入物周围解剖结构的可见性方面的差异。结果CS-SEMAC在T1、T2矢状位图像上金属伪影面积分别为(15.45±6.84)、(22.23±9.76)cm²,显著低于其他两种序列,差异具有统计学意义(P<0.001);三种序列在T2抑脂矢状面图像上的SNR两两比较显示:HBW序列椎体SNR显著高于其他两种序列,Dixon序列椎体SNR显著低于其他两种序列,CS-SEMAC序列椎体SNR低于HBW序列,高于Dixon序列,差异均有统计学意义(P<0.001);在图像清晰度上,T2WI-tirm-CS-SEMAC序列评分低于其他两种序列,差异具有统计学意义(P<0.001);T2WI-tirm-CS-SEMAC序列在图像质量和脂肪抑制效果方面评分显著优于其他两种序列,差异具有统计学意义(P<0.001);并且CS-SEMAC序列相较于其他两种序列更能清晰显示植入物周围椎体、椎弓根、椎间孔及神经根,差异具有统计学意义(P<0.001)。结论CS-SEMAC序列相比于HBW、Dixon序列能够有效减少植入物周围的金属伪影,并且能显著提高T2抑脂序列的图像质量和脂肪抑制效果,虽然在T2抑脂上金属植入物邻近椎体SNR相比HBW序列有所下降,图像比HBW和Dixon图像略模糊,但是椎体周围关键解剖结构的可见度明显提升,对脊柱术后解剖结构的显示有一定优势。

Objective:To investigate the value of compressed sensing combined with compressed sensing-slice-encoding metal artifact correction(CS-SEMAC)technique for postoperative MRI of spinal metal implants.Materials and Methods:The 3.0 T sagittal MRI CS-SEMAC sequence,high bandwidth(HBW)sequence,and water-fat separation(Dixon)sequence were compared in terms of metal implant artifact area,vertebral signal-to-noise ratio(SNR),image quality,image clarity,fat suppression effect,and visibility of anatomical structures around the implant in 35 postoperative spinal metal implant patients with inclusion criteria.Results:The metal artifact areas of CS-SEMAC on T1 and T2 were(15.45±6.84)and(22.23±9.76)cm²,respectively,which were significantly lower than those of the other two sequences,and the differences were statistically significant(P<0.001);Two-by-two comparison of signal-to-noise ratios of the three sequences on the T2 lipid-suppressed sagittal images showed that:the vertebral snr of the HBW sequence was significantly higher than those of the two other sequences,Dixon sequence SNR was significantly lower than the other two sequences,and CS-SEMAC sequence SNR was lower than the HBW sequence and higher than the Dixon sequence,and the differences were all statistically significant(P<0.001);In terms of image clarity,the score of the T2WI-tirm-CS-SEMAC sequence was lower than that of the other two sequences,and the difference was statistically significant(P<0.01).The T2WI-tirm-CS-SEMAC sequence scored significantly better than the other two sequences regarding the image quality and fat suppression effect(P<0.001);The T2WI-tirm-CS-SEMAC sequence could clearly display the vertebral body,pedicle,intervertebral foramen and nerve roots around the implant(P<0.001);meanwhile.The T2WI-Dixon lipoinhibition sequence could also clearly display the nerve roots in the intervertebral foramen,and the difference was statistically significant(P<0.001).Conclusions:Compared with HBW and Dixon sequences,CS-SEMAC sequence can effectively reduce the metal artifacts around the implant,and significantly improve the image quality and fat inhibition effect of T2 lipid suppression sequence.Although the SNR of the adjacent vertebral body of the metal implant on T2 lipid suppression is decreased compared with that of HBW sequence,the image is slightly blurred than that of HBW and Dixon images.However,the visibility of key anatomical structures around the vertebral body is significantly improved,which has certain advantages for the display of spinal anatomy after spinal surgery.