Impact of the Static and Radiofrequency Magnetic Fields Produced by a 7T MR Imager on Metallic Dental Materials
Impact of the Static and Radiofrequency Magnetic Fields Produced by a 7T MR Imager on Metallic Dental Materials
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DOI：
10.2463/mrms.2014-0122
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发表时间：
2016-01-01
影响因子：
3
通讯作者：
Kondo, Hisatomo
中科院分区：
文献类型：
--
作者：
Oriso, Kenta;Kobayashi, Takuya;Kondo, Hisatomo
目的：我们在 7 特斯拉的磁共振 (MR) 成像中检查了与各种金属牙科材料的存在相关的安全问题。方法：使用 7T MR 成像扫描仪检查 18 种材料，包括 8 种用于牙科修复的金属、6 种骨整合牙种植体、2 种牙种植体基台和 2 种磁性附着保持器。我们通过在定制仪器上读取偏转角来评估静磁场和材料之间的平移吸引力，并与 3T 下的偏转角进行比较。通过使用光纤温度计测量琼脂糖凝胶体模中的相关温度变化，检查了使用 6 个不同序列进行图像采集期间射频的热效应。结果：金属牙科材料的偏转角在 7T 时明显大于 3T。在全金属冠 (FMC) 中，钴铬 (Co-Cr) 合金的偏转角为 18.0 度，镍铬 (Ni-Cr) 合金的偏转角为 13.5 度，其他材料的偏转角为 0 度。牙种植体和基台的偏转角最小，范围为 5.0 至 6.5 度，而磁性附着保持器强烈吸引到磁场，偏转角为 90 度或更大。每个序列中 FMC 的温度升高都很显着，但升高幅度均小于 1 摄氏度。与其他牙种植体和基台相比，长度为 50 毫米的牙种植体显示出显着但温和的温度升高（高达 1.5 摄氏度），特别是在具有高比吸收率值的序列上。 结论：虽然大多数金属牙科材料在 7T 下没有表现出明显的平移吸引力或加热，但磁性附着保持器上的巨大吸引力表明对接受 MR 成像检查的患者和研究参与者存在潜在风险。
Purpose: We examined safety issues related to the presence of various metallic dental materials in magnetic resonance (MR) imaging at 7 tesla.Methods: A 7T MR imaging scanner was used to examine 18 kinds of materials, including 8 metals used in dental restorations, 6 osseointegrated dental implants, 2 abutments for dental implants, and 2 magnetic attachment keepers. We assessed translational attraction forces between the static magnetic field and materials via deflection angles read on a tailor-made instrument and compared with those at 3T. Heating effects from radiofrequency during image acquisitions using 6 different sequences were examined by measuring associated temperature changes in agarose-gel phantoms with a fiber-optic thermometer.Results: Deflection angles of the metallic dental materials were significantly larger at 7T than 3T. Among full metal crowns (FMCs), deflection angles were 18.0 degrees for cobalt-chromium (Co-Cr) alloys, 13.5 degrees for nickel-chromium (Ni-Cr) alloys, and 0 degrees for other materials. Deflection angles of the dental implants and abutments were minimal, ranging from 5.0 to 6.5 degrees, whereas the magnetic attachment keepers were strongly attracted to the field, having deflection angles of 90 degrees or more. Increases in temperature of the FMCs were significant but less than 1 degrees C in every sequence. The dental implant of 50-mm length showed significant but mild temperature increases (up to 1.5 degrees C) when compared with other dental implants and abutments, particularly on sequences with high specific absorption rate values.Conclusion: Although most metallic dental materials showed no apparent translational attraction or heating at 7T, substantial attraction forces on the magnetic attachment keepers suggested potential risks to patients and research participants undergoing MR imaging examinations.