颈椎后路钛合金脊柱内固定系统对术后MRI成像的影响

Influence on magnetic resonance image of posteiror titanium cervical internal fixation system

[目的]探讨颈椎后路钛合金内固定系统对术后MRI成像的影响。[方法]对6例行颈椎后路钛合金脊柱内固定的患者术后进行MRI检查,所用MRI为1.0 T及1.5 T的超导MRI系统,患者均进行矢状位的快速自旋回波序列（TSE）T1加权像（T1WI）和TSE T2加权像（T2WI）以及轴位的TSET1加权像扫描,然后对术后钛合金内固定的伪影特点及其对椎管内结构的影响进行分析。[结果]MRI伪影的大小为内固定大小的2~3倍,基本能够辨认出原来内固定物的形状,钛合金内固定植入物本身在T1和T2加权上都表现为低信号,其边缘在T1和T2加权上都有明确分界线的高信号区。在矢状面T1和T2加权和轴位T1加权上均可清晰显示脊髓和椎管内的结构。后路系统的连接棒伪影较小,只对紧邻的椎板和小关节处图像辨认有影响,对术后图像观察的影响较小。椎板钩的伪影较大,会影响对椎板附近结构的观察,特别是伸入椎管内的部分会影响对脊髓后部的观察。椎弓根螺钉钉尾部伪影较大,对紧邻的椎板和小关节处图像辨认有影响;正确植入的颈椎弓根螺钉伪影也较大,主要会影响对邻近部位椎管侧方、椎动脉、椎间孔、脊神经和后外侧突出的椎间盘等结构的观察。[结论]颈椎后路脊柱钛合金内固定术后患者进行MRI检查时,应该尽量选择快速自选回波序列进行扫描,当使用常规自旋回波序列扫描时,应尽量减少TE。医生在分析术后MRI图像时应该充分认识到钛合金内固定的伪影对图像的影响,以去伪存真,结合患者的临床表现作出正确的判断。

[Objective]To discuss the influence of posterior cervical titanium internal fixation system on magnetic resonance image（MRI）.[Method]Six cases that had operated in Changhai hospital with posterior cervical titanium internal fixation system performed MRI scan.The MRI system were 1.0-T or 1.5-T scanner.Patients all performed sagital T1,T2 and axial T1-weighted image scan under turbo spin echo（TSE）sequence,then the artifacts and its influence on the MRI image were analyzed.[Result]Mean artifact size ranged from 2 to 3 times of actual screw size.The artifact was similar to the primary shape of internal fixation system with low intensity signal on center and high intensity signal on the margin.The details in the spinal canal can be distinguished.The rod had small artifact,but the laminar hook had large artifact which obscured the posterior structure of spinal canal,and the artifact of pedicle screw had influence on lateral spinal canal,nerve root and vertebral artery.[Conclusion]Patients with posterior cervical titanium internal fixation system should choose Turbo spin echo（TSE）sequence for MRI scan,if the spin echo is performed,the TE should be minimized.