不同牙位金属桩核冠MRI图像伪影比较研究

Comparative study on magnetic resonance imaging artifacts of oral metal post-core-crown at different teeth

目的探讨不同牙位镍铬合金桩核冠MRI图像时伪影大小,以更好地指导临床对材料的选取。方法选用镍铬合金分别制成左上1(前牙)、6(后牙)标准桩核冠模型做为实验组,将模型固定于水模中。应用1.5 T MRI扫描仪,头线圈,对桩核冠模型行横断面、矢状面、冠状面T2加权成像(T2WI)扫描。确定伪影最大的层面并测量伪影面积。应用SAS V8统计学软件进行数据分析。结果横断面、矢状面、冠状面之间金属伪影大小不同,其差异有统计学意义(F=9.51,P<0.05)。与测量层面相对应的前后牙在横断面、冠状面、矢状面的实际截面积分别为:前牙(0.73±0.05)cm^2、(0.43±0.06)cm^2、(0.43±0.04)cm^2;后牙(0.67±0.06)cm^2、(1.14±0.05)cm^2、(0.49±0.06)cm^2。前后牙在横断面、冠状面、矢状面伪影面积分别为:前牙(3.88±0.22)cm^2、(3.11±0.37)cm^2、(3.93±0.33)cm^2;后牙(8.44±0.58)cm^2、(7.18±0.41)cm^2、(8.52±0.20)cm^2。在横断面、矢状面、冠状面图像中,后牙比前牙金属伪影大(P<0.01)。结论在保证美观、结实的情况下,要尽可能减小金属牙冠、金属核的体积,在保证固位力的情况下,减小桩钉的长度和直径,来减小金属伪影。

Objective To investigate the size of Ni-Cr alloy post-core-crown MR artifacts at different teeth, and provide guidance for clinical material selection. Methods Ni-Cr alloy were molded into standard post-core-crown anterior tooth and posterior tooth model, and phantom were fixed in water modeling. The Ni-Cr alloy post-core-crown model were scanned by1.5 T MR scanner with head coil, the axial, sagittal and coronal T2 WI sequence was scanned, respectively. The section of the largest artifacts was determined and measured the area, and the statistical testing was carried out. Results The artifacts size of axial, sagittal and coronal were different at different section（F = 9.51, P〈0.05）. Compared with measured plane, the actual section area of axial, coronal and sagittal plane were as follows： anterior tooth（0.73 ± 0.05） cm^2,（0.43 ± 0.06） cm^2,（0.43 ± 0.04） cm^2;posterior tooth（0.67 ± 0.06） cm^2,（1.14 ± 0.05） cm^2,（0.49 ± 0.06） cm^2. The artifacts area of axial, coronal and sagittal plane were as follows： anterior tooth（3.88 ± 0.22） cm^2,（3.11 ± 0.37） cm^2,（3.93 ± 0.33） cm^2; posterior tooth（8.44 ± 0.58） cm^2,（7.18 ± 0.41） cm^2,（8.52 ± 0.20） cm^2. The artifacts of axial, sagittal and coronal in posterior tooth were bigger than those in anterior tooth（P〈0.01）.Conclusion It is demonstrated that the volume of metal crown and core should be minimized for ensuring beauty and durability, and less length and diameter of pegs for ensuring retention to decrease artifacts.