MR成像参数对口腔金属材料伪影作用的实验研究

Metallic Artifacts Caused by Dental Materials in MR imaging:Effects of Imaging Parameters

目的:比较GRE、SE和FSE序列中,不同序列参数对口腔金属材料伪影的影响。方法:选择口腔常用钛合金和金合金材料分别制成标准冠模型,在1.5T的场强中进行梯度回波序列(gradient recalled echo,GRE)、自旋回波序列(spin echo,SE)和快速自旋回波序列(fast spin echo,FSE)成像。调节成像参数回波时间(echo time,TE)、带宽(bandwidth,BW)、视野(field of view,FOV)和矩阵(matrix),测量各模型的伪影面积,统计学处理采用方差分析和t检验。结果:GRE和SE序列中,伪影面积随TE改变而改变,差别有统计学意义(P<0.05),TE延长,伪影增加;GRE和FSE序列中,FOV减小,伪影降低,差异有统计学意义(P<0.05);增加SE、FSE序列带宽值,伪影减小(P<0.05);而矩阵增加时,仅GRE序列中的钛合金伪影减小,差异有统计学意义(P<0.05)。结论:调节成像参数可以在一定程度上控制金属伪影的影响:减小TE和FOV,增加BW和矩阵,有利于减小金属伪影。但同时也发现,各成像序列对不同参数的敏感程度也不一致。

Objective： To determine the optimal MR-imaging parameters for minimization of metallic artifacts caused by dental materials. Methods： Titanium and golden alloy made experimental phantoms were imaged with a 1.5T scanner using 3 sequences including gradient recalled echo（GRE）, spin echo（SE） and fast spin echo（FSE）. Echo time（TE）, bandwidth（BW）, field of view（FOV） and matrix varied. Artifact area was measured for each phantom and sequence. Analysis of variance and t-test was done. Results： Artifact area increased significantly （P 〈0.05） when TE became longer in GRE and SE sequences. Decreases in artifact area correlated with a reduction of FOV in GRE and FSE sequences （P〈0. 05）. When we increased BW in SE and FSE sequences, artifact area decreased （P〈0.05）. But with increase of matrix, only artifact caused by titanium alloy became significantly smaller in GRE sequence （P〈0. OS）. Conclusion： Except for materials and sequences studied before by many other investigators, in this research we found artifacts caused by dental materials also depended on some imaging parameters. Artifact area was reduced by the use of shorter TE, smaller FOV, larger BW and matrix, but different sequences were sensitive to different parameters.