不同磁场强度下镍铬合金固定修复体MRI伪影的比较

Comparison of MRI artifacts caused by Ni-Cr alloy fixed prostheses on different field-strength magnets

目的探讨不同磁场强度(1.5T和3.0 T)对镍铬合金固定修复体磁共振成像(MRI)中伪影的影响。方法以镍铬合金制作不同厚度的单冠、桥修复体及上半口修复体作为试样,置于盛有清水的容器中央,分别于1.5 T和3.0 T的磁场强度下进行MR扫描,勾画和计算伪影面积并进行比较分析,以相同形状和厚度的塑料修复体作为对照修复体。结果镍铬合金固定修复体在MRI中均可产生伪影,其面积随修复体体积的增加而扩大,而对照修复体未见伪影形成。与1.5 T MRI相比,3.0 T MRI上产生的伪影面积显著增大(P<0.05);相同磁场强度下,与扫描序列T_2WI相比,扫描序列T_1WI上所形成的伪影面积显著增大(P<0.05)。结论口腔内有镍铬合金固定修复体的患者在行MRI检查时,应选择较低的磁场强度及快速自旋回波序列进行扫描。应避免选用镍铬合金制作大范围固定修复体。

Objective To evaluate the influence of different field-strength magnets （1.5 T and 3.0 T） on MRI artifacts caused by Ni-Cr alloy fixed prostheses. Methods The crown, bridge and upper denture fixed prostheses with different thickness were produced by Ni-Cr alloy as test samples, and were one by one put on the centre of water phantom for MR scanning with different field-strength magnets （1.5 T and 3.0 T）. The artifact areas on these two field-strength magnets were measured and statistically compared. The plastic prostheses with the same shape and thickness as the test samples were served as controls. Results Ni-Cr alloy fixed prostheses could cause MRI artifacts, and the artifact areas increased with the mass of prostheses. However, no artifact area was found in controls. Compared with those on 1.5 T magnet, the MRI artifact areas significantly increased on 3. 0 T magnet （ P 〈 0.05）. Under the same field-strength, the artifact areas significantly increased by scanning sequence T1WI than those by T2WI （P 〈 0.05）. Conclusion The lower field strength and fast spin echo sequence should be selected for MRI examinations in patients wearing fixed prostheses made of Ni-Cr alloy. Ni-Cr alloy should be avoided for the fixed prostheses of big mass.