金合金铸造冠磁共振成像特点的实验研究

MR images affected by gold alloy casting crown: an experimental study

目的 比较金合金铸造冠与镍铬合金铸造冠在磁共振成像时的差异。 方法 以猴为实验动物 ,采用其右侧上颌侧切牙分别制作、配戴金合金及镍铬合金铸造冠 ,用 2 0TPrestigeMRI扫描仪按临床常规进行 5个常用序列 (T1:自旋回波T1回权像 ;T2 :快速自旋回波T2 加权像 ;PD :快速自旋回波质子密度像 ;GRE :梯度回波T1加权像 ;GEEPI:单次激发平面回波成像 )的头颈部扫描 ,观察两种合金铸造冠对图像的影响。 结果 金合金冠无明显伪影形成 ;镍铬合金冠周围组织的影像在T1、T2 、PD、GRE畸变为近似圆形的低信号伪影 ,在GEEPI畸变为不规则的片状信号失落 ;GRE影像畸变 (伪影 )涉及 6个扫描层面 ,最大直径约 19mm。 结论 金合金修复体不影响MRI检查的准确性 ;镍铬合金修复体使其毗邻组织的磁共振成像发生畸变 ,其累及范围和影响程度因扫描序列而异。

Objective To compare the effects of the gold alloy casting crown with Ni-Cr alloy crown on MR images. Methods A casting gold alloy crown and a Ni-Cr alloy crown were put on a narcotized monkey's right upper lateral incisor respectively. Then the monkey's head-and-neck was examined with a 2.0 T MR scanner. Four clinical routine scan sequences including spin echo (T 1), fast spin echo (T 2), proton density (PD), gradient echo (GRE) and one functional scan protocol (gradient echo planar image, GE EPI) were used to observe the effects of the gold alloy crown and the Ni-Cr alloy crown. Results 1.The gold alloy casting crown created no artifact during all the 5 scans. 2. Metal artifact around the crown was found on all images with different size and shape. On the T 1, T 2, PD, and GRE images, the artifacts were circular. On the GE EPI images, those were patch-shaped. On GRE images, artifact was found in 6 slices, and maximal artifact was approximately 19 mm in diameter. Conclusions 1.Gold alloy restorer does not affect the veracity of MRI examination.2. Ni-Cr alloy restorer results in distortion on all MR images. The distortion is different according to the scan sequence.