General Electric Global Research, Imaging Technologies, Niskayuna, New York, USA.
J Magn Reson Imaging. 2011 May;33(5):1209-17. doi: 10.1002/jmri.22544.
To use electromagnetic (EM) simulations to study the effects of body type, landmark position, and radiofrequency (RF) body coil type on peak local specific absorption rate (SAR) in 3T magnetic resonance imaging (MRI).
Numerically computed peak local SAR for four human body models (HBMs) in three landmark positions (head, heart, pelvic) were compared for a high-pass birdcage and a transverse electromagnetic 3T body coil. Local SAR values were normalized to the IEC whole-body average SAR limit of 2.0 W/kg for normal scan mode.
Local SAR distributions were highly variable. Consistent with previous reports, the peak local SAR values generally occurred in the neck-shoulder area, near rungs, or between tissues of greatly differing electrical properties. The HBM type significantly influenced the peak local SAR, with stockier HBMs, extending extremities towards rungs, displaying the highest SAR. There was also a trend for higher peak SAR in the head-centric and heart-centric positions. The impact of the coil types studied was not statistically significant.
The large variability in peak local SAR indicates the need to include more than one HBM or landmark position when evaluating safety of body coils. It is recommended that an HBM with arms near the rungs be included to create physically realizable high-SAR scenarios.
利用电磁场（EM）模拟研究体型、标记位置和射频（RF）体线圈类型对 3T 磁共振成像（MRI）中峰值局部比吸收率（SAR）的影响。
比较了三种标记位置（头部、心脏、骨盆）的四个人体模型（HBM）在高通鸟笼和横向电磁 3T 体线圈中的数值计算峰值局部 SAR。将局部 SAR 值归一化为正常扫描模式下 IEC 全身平均 SAR 限值 2.0 W/kg。
局部 SAR 分布高度可变。与先前的报告一致，峰值局部 SAR 值通常出现在颈部-肩部区域、靠近横档处或电特性差异很大的组织之间。HBM 类型对峰值局部 SAR 有显著影响，四肢较粗、向横档延伸的 HBM 显示出最高的 SAR。头部中心和心脏中心位置的峰值 SAR 也有升高的趋势。所研究的线圈类型的影响没有统计学意义。
峰值局部 SAR 的较大变化表明，在评估体线圈的安全性时，需要包括多个 HBM 或标记位置。建议包括手臂靠近横档的 HBM，以创建物理可实现的高 SAR 情况。
