Probabilistic analysis of the specific absorption rate intersubject variability safety factor in parallel transmission MRI
Probabilistic analysis of the specific absorption rate intersubject variability safety factor in parallel transmission MRI
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DOI：
10.1002/mrm.26468
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发表时间：
2017-09-01
影响因子：
3.3
通讯作者：
Boulant, Nicolas
中科院分区：
文献类型：
--
作者：
Le Garrec, Morgane;Gras, Vincent;Boulant, Nicolas
目的：在通用模型上进行电磁模拟，计算平行传输中的特定吸收率（SAR）。在这项研究中，我们提出了一个概率分析来研究安全系数，用于解释7T时头部成像的SAR主体间变异性和风险关系。方法采用33种有限元电磁模拟方法，对头长、头宽和Z、Y随机变量位移组成的四维参数空间进行采样。基于各构型的SAR矩阵，对不同类型的射频脉冲重构了SAR随参数变化的多元二阶多项式。然后进行蒙特卡罗计算以计算给定SAR值发生的概率。结果通过对大量射频激励脉冲的测试，发现在给定研究参数的情况下，将安全裕度放大1.5的平均模型计算的SAR返回的概率小于1%，超过了成年高加索人群。结论本文提出的研究SAR主体间变异性的方法使用了合理数量的电磁模拟。未来的SAR安全边际可以根据风险/收益比评估来推断。中西医结合杂志（英文版），2017。(c) 2016年国际医学磁共振学会。
PurposeSpecific absorption rate (SAR) calculations in parallel transmission are commonly performed by using electromagnetic simulations on generic models. In this study, we propose a probabilistic analysis to study the safety factor employed to account for SAR intersubject variability versus risk relationship in head imaging at 7T.MethodsThirty-three finite-element electromagnetic simulations were conducted to sample the four-dimensional parameter space consisting of the head length, head breadth, and shifts in Z and Y random variables. Based on the SAR matrices for each configuration, a multivariate second-order polynomial of the SAR versus the different parameters was reconstructed for different types of radiofrequency pulses. A Monte Carlo calculation was then performed to compute the probability of occurrence of a given SAR value.ResultsBy testing a large number of radiofrequency excitation pulses, the SAR calculated for the average model amplified by a safety margin of 1.5 was found to return a probability of less than 1% to be exceeded across the adult Caucasian population given the investigated parameters.ConclusionThe proposed method to study SAR intersubject variability uses a reasonable number of electromagnetic simulations. Look-ahead SAR safety margins can be deduced based on risk/benefit ratio assessments. Magn Reson Med 78:1217-1223, 2017. (c) 2016 International Society for Magnetic Resonance in Medicine.