颈椎钛合金固定术后MRI优化扫描

MRI optimization scanning of cervical spine with titanium alloy internal fixation

目的:探讨颈椎钛合金术后MRI扫描参数的优化,以降低磁化率伪影。方法:提出以分组的方式,按照3级评分标准,对10例颈椎钛合金术后患者行MRI检查(5例前路固定,5例后路固定),患者均行矢状位、轴位:T1,T2加权成像(T1WI,T2WI)。其中部分扫描改变频率编码方向,TE值,空间分辨率,序列进行对比。分别对各组图像中磁化率伪影大小进行评判。结果:伪影在T1、T2加权像均呈低信号,其边缘分界线呈高信号;频率编码方向与钛合金长轴主轴平行时产生的伪影小于两者垂直时;TE取值越小,伪影越轻微;分辨率越高,伪影越轻微;梯度回波伪影比快速自选回波伪影严重。结论:在不增加病人风险的前提下,选择合适的扫描序列,合理优化扫描参数,可以有效降低磁化率伪影。

Objective To discuss how to optimize MRI scanning parameters of cervical spine with titanium alloy internal fixation,and reduce susceptibility artifacts.Methods 10 patients with cervical spine titanium alloy fixation were performed MRI（five cases with anterior fixation,five cases with posterior fixation）,all of them were performed T1WI and T2WI in both sagittal and transverse directions.Among them,some scans were changed the frequency-encoding directions,the value of TE,spiral resolution and sequence respectively;and all the images were assessed comparatively in a blinded fashion by three expert radiologists.Results The susceptibility artifacts in image were bigger than the titanium alloy,and they were low intensity signal in the T1WI and T2WI,and high intensity signal on the margin.The susceptibility artifacts become greater when the direction of frequency-encoding gradient was changed from parallel to the direction of the titanium screw＇s long axial to perpendicular;when the value of TE became smaller,artifacts became lighter;when the spiral resolution became higher,the artifacts became lighter;the artifacts obtained from GRE were more serious than FSE.Conclusion The susceptibility artifacts in the direction that the encoding depends on frequency are more serious,so the interested field should not be covered by the artifact in the frequency encoding and slice-select directions.Without increasing the risk of patients,the susceptibility artifacts in cervical spine MRI scan with titanium alloy internal fixation can be reduced by selecting suitable scanning sequences and optimizing the scan parameters..