Whole-Body and Local RF Absorption in Human Models as a Function of Anatomy and Position within 1.5T MR Body Coil
Whole-Body and Local RF Absorption in Human Models as a Function of Anatomy and Position within 1.5T MR Body Coil
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DOI：
10.1002/mrm.24690
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发表时间：
2014-02-01
影响因子：
3.3
通讯作者：
Kuster, Niels
中科院分区：
文献类型：
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作者：
Murbach, Manuel;Neufeld, Esra;Kuster, Niels
目的磁共振成像中的射频能量沉积必须受到限制，以防止患者过度加热。本文研究了射频吸收与大尺度解剖特征（如身高）的相关性。理论与方法特定吸收率（SAR）作为量化射频吸收的关键参数，随患者桡骨尺寸的增加而增加，从而随大尺度解剖特性的增加而增加。六个人体模型的吸收能量在1.5T的身体线圈中以不同的z形位置（头到膝盖）建模。结果对于固定的B1+入射场，肥胖成人模型的全身SAR可高达儿童的2.5倍（局部SAR高达7倍）。如果暴露归一化为4 W/kg全身SAR，则局部SAR可以远远超过局部发射线圈的限制，并显示出主体间的变化，最高可达三倍。结论解剖结构与诱导局部SAR的相关性在归一化暴露条件下较弱，但在固定B1+场条件下较强，表明解剖特性可用于快速预测SAR。研究结果表明，具有代表性的虚拟人口是研究区域SAR水平的必要条件。中华医学杂志，2014,31(1):559 - 559。(c) 2013 Wiley Periodicals, Inc.；
PurposeRadiofrequency energy deposition in magnetic resonance imaging must be limited to prevent excessive heating of the patient. Correlations of radiofrequency absorption with large-scale anatomical features (e.g., height) are investigated in this article.Theory and MethodsThe specific absorption rate (SAR), as the pivotal parameter for quantifying absorbed radiofrequency, increases with the radial dimension of the patient and therefore with the large-scale anatomical properties. The absorbed energy in six human models has been modeled in different Z-positions (head to knees) within a 1.5T bodycoil.ResultsFor a fixed B1+ incident field, the whole-body SAR can be up to 2.5 times higher (local SAR up to seven times) in obese adult models compared to children. If the exposure is normalized to 4 W/kg whole-body SAR, the local SAR can well-exceed the limits for local transmit coils and shows intersubject variations of up to a factor of three.ConclusionsThe correlations between anatomy and induced local SAR are weak for normalized exposure, but strong for a fixed B1+ field, suggesting that anatomical properties could be used for fast SAR predictions. This study demonstrates that a representative virtual human population is indispensable for the investigation of local SAR levels. Magn Reson Med 71:839-845, 2014. (c) 2013 Wiley Periodicals, Inc.