Toward Individualized SAR Models and In Vivo Validation
Toward Individualized SAR Models and In Vivo Validation
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DOI：
10.1002/mrm.22948
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发表时间：
2011-12-01
影响因子：
3.3
通讯作者：
Graesslin, I.
中科院分区：
文献类型：
--
作者：
Homann, H.;Boernert, P.;Graesslin, I.
比吸收率（SAR）是高场MRI序列设计中的限制性约束。SAR估计通常通过使用通用人体模型的数值模拟来执行。这必然导致目前SAR预测的内在不确定性。本研究首先调查所需的人体模型的空间分辨率和所需的软组织类的数量方面的细节，基于有限差分时域模拟的3 T体线圈。数值结果表明，分辨率为5毫米是足够的局部SAR估计。此外，发现脂肪组织、富水组织和肺之间的区别对于表示人体内的涡流路径至关重要。然后，本研究提出了一种新的方法，用于从全身水脂肪分离的MR数据生成个性化的身体模型，并将其应用于志愿者。SAR热点始终发生在手臂中，因为靠近体线圈以及肌肉的狭窄区域。与测量的B（1）场图相比，模拟场的初始体内验证显示出良好的定性和定量一致性。Magn Reson Med 66：1767-1776，2011。(C)2011 Wiley Periodicals，Inc.
The specific absorption rate (SAR) is a limiting constraint in sequence design for high-field MRI. SAR estimation is typically performed by numerical simulations using generic human body models. This entails an intrinsic uncertainty in present SAR prediction. This study first investigates the required detail of human body models in terms of spatial resolution and the number of soft tissue classes required, based on finite-differences time-domain simulations of a 3 T body coil. The numerical results indicate that a resolution of 5mm is sufficient for local SAR estimation. Moreover, a differentiation between fatty tissues, water-rich tissues, and the lungs was found to be essential to represent eddy current paths inside the human body. This study then proposes a novel approach for generating individualized body models from whole-body water-fat-separated MR data and applies it to volunteers. The SAR hotspots consistently occurred in the arms due to proximity to the body coil as well as in narrow regions of the muscles. An initial in vivo validation of the simulated fields in comparison with measured B(1)-field maps showed good qualitative and quantitative agreement. Magn Reson Med 66:1767-1776, 2011. (C) 2011 Wiley Periodicals, Inc.