磁性附着体的衔铁对磁共振成像的影响

Impact of magnetic attachment keepers on magnetic resonance imaging examination

目的:研究磁性附着体的衔铁对磁共振成像的影响。方法:体外实验选用MAGFIT EX400,MAGFITEX600及MAGNEDISC 800型磁性附着体的衔铁,分别设计为不铸接、与镍铬合金铸接和与金钯合金铸接3种形式,并完成衔铁根帽的制作。体内实验选择需行磁性附着体可摘义齿修复的患者作为研究对象。用SiemensSONATA1.5-T磁共振仪对所有样本及研究对象进行扫描,对体外样本伪影最大径进行测量和比较,对体内实验的伪影对头颈部解剖结构成像的影响进行分析。结果:MAGFIT EX400型、MAGFIT EX600型及MAGNEDISC 800型衔铁的伪影最大纵径分别为158.94、168.52和173.00 mm。衔铁伪影对颏部、舌、唇、软硬腭、颌骨的磁共振成像造成明显影响,位于后牙区的衔铁对脑及脊髓的成像造成影响。采用SE序列及左右向的频率编码,可以减小衔铁对头颈部MRI的影响。结论:磁性附着体的衔铁对磁共振成像有明显影响。

Objective：To evaluate the effects of magnetic attachment keepers on MRI images.Me-thods：In in vitro part,keepers of MAGFIT EX 400,MAGFIT EX 600 and MAGNEDISC 800 magnetic attachment systems were cast into standard root-caps with different alloy respectively,including nickel-chromium alloy and gold-palladium alloy,or not be cast for contrast.In in vivo part,volunteers with keepers in different position and amount were included.All the specimens and volunteers were imaged by a Siemens SONATA 1.5-T MRI scanner.Extent of the artifacts in every slice was measured.The magnitude of the artifacts and the distortion of the anatomic structures were compared.Results：All kinds of keepers being studied produced obvious MRI artifacts.The extent of MRI artifacts induced by MAGFIT EX 400 keepers,MAGFIT EX 600 keepers and MAGNEDISC 800 keepers are 158.94 mm,168.52 mm and 173.00 mm,respectively.The images of mental region,tongue,palate,jawbone and sinus were evidently obscured by artifacts in all cases.When keeper was put in the molar region,the keeper-related MRI artifact may obscure the imaging of brain,spinal cord.SE sequence with right-left frequency-encoding direction was more desirable in MRI for the patients with magnetic attachment keepers.Conclusion：Keepers of magnetic attachment system did induce obvious artifacts in MRI examination.