Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations
Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations
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身体循环相关 MRI 射频引起的加热危害：观察、特征和建议
DOI：
10.1002/mrm.28954
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发表时间：
2021
影响因子：
3.3
通讯作者：
Chen, Ji
中科院分区：
文献类型：
--
作者：
Yang, Xiaolin;Zheng, Jianfeng;Wang, Yu;Long, Stuart A.;Kainz, Wolfgang;Chen, Ji
目的评估1.5T MR系统中由体环姿势引起的射频致热危害。方法基于可摆姿势的成年男性模型创建12个具有不同体环姿势的高级高分辨率解剖学上正确的人体模型。进行数值模拟，以评估这12个模型在11个标志处的射频（RF）致热。开发定制体模以验证数值模拟并定量分析影响射频致热的因素，例如接触面积、线圈尺寸和加载位置。测量了三种不同姿势的体模内的RF感应加热。ResultsThe RF感应加热从体环姿势可以高达11倍高于从原来的姿势。RF感应产热随着体环尺寸的增加和接触面积的减小而增加。当体环中心和射频线圈等中心彼此接近时，磁通量增加，导致射频感应加热增加。在体环中产生的气隙或产生平行于体环的极化磁场可以将发热减少至少三倍。实验测量提供，验证数值结果的正确性。ConclusionSafe患者的姿势在MR检查建议使用绝缘材料，以防止环路的形成，从而避免高RF感应加热。如果无法避免体环，则应将体环放置在射频发射线圈外部。此外，磁场平行于体环的线性极化可用于规避高射频致热。
PurposeTo assess RF‐induced heating hazards in 1.5T MR systems caused by body‐loop postures.MethodsTwelve advanced high‐resolution anatomically correct human body models with different body‐loop postures are created based on poseable human adult male models. Numerical simulations are performed to assess the radiofrequency (RF)‐induced heating of these 12 models at 11 landmarks. A customized phantom is developed to validate the numerical simulations and quantitatively analyze factors affecting the RF‐induced heating, eg, the contact area, the loop size, and the loading position. The RF‐induced heating inside three differently posed phantoms is measured.ResultsThe RF‐induced heating from the body‐loop postures can be up to 11 times higher than that from the original posture. The RF‐induced heating increases with increasing body‐loop size and decreasing contact area. The magnetic flux increases when the body‐loop center and the RF coil isocenter are close to each other, leading to increased RF‐induced heating. An air gap created in the body loop or generating a polarized magnetic field parallel to the body loop can reduce the heating by a factor of three at least. Experimental measurements are provided, validating the correctness of the numerical results.ConclusionSafe patient posture during MR examinations is recommended with the use of insulation materials to prevent loop formation and consequently avoiding high RF‐induced heating. If body loops cannot be avoided, the body loop should be placed outside the RF transmitting coil. In addition, linear polarization with magnetic fields parallel to the body loop can be used to circumvent high RF‐induced heating.
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发表时间：
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期刊：
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