Xia Meiqi, Zheng Jianfeng, Yang Rui, Song Shuo, Xu Jian, Liu Qi, Kainz Wolfgang, Long Stuart A, Chen Ji
Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA.
UIH America Inc, Houston, Texas, USA.
Magn Reson Med. 2021 Mar;85(3):1669-1680. doi: 10.1002/mrm.28514. Epub 2020 Sep 24.
This paper studies the RF-induced heating for modular external fixation devices applied on the leg regions of the human bodies. Through numerical investigations of RF-induced heating related to different patient orientations, landmark positions, and device positions under 1.5T and 3T MRI systems, simple and practical methods to reduce RF-induced heating are recommended.
Numerical simulations using a full-wave electromagnetic solver based on the finite-difference time-domain method were performed to characterize the effects of patient orientations (head-first/feet-first), landmark positions (the scanning area of the patient), and device positions (device on left or right leg) on the RF-induced heating of the external fixation devices. The G32 coil design and three anatomical human models (Duke model, Ella model, and Fats model) were adopted to model the MRI RF coil and the patients.
The relative positions of the patient, device, and coil can significantly affect the RF-induced heating. With other conditions remaining the same, changing the device position or patient orientation can lead to a peak 1-g averaged spatial absorption ratio variation of a factor around four. By changing the landmark position and the patient orientation, the RF-induced heating can be reduced from 1323.6 W/kg to 217.5 W/kg for the specific scanning situations studied.
Patient orientations, landmark positions, and device positions influence the RF-induced heating of modular external fixation devices at 1.5 T and 3 T. These features can be used to reduce the RF-induced heating during MRI simply and practically.
本文研究应用于人体腿部区域的模块化外固定装置的射频感应加热情况。通过对1.5T和3T磁共振成像（MRI）系统下不同患者体位、体表标志位置和装置位置相关的射频感应加热进行数值研究，推荐简单实用的减少射频感应加热的方法。
使用基于时域有限差分法的全波电磁求解器进行数值模拟，以表征患者体位（头先入/脚先入）、体表标志位置（患者扫描区域）和装置位置（装置在左腿或右腿）对外部固定装置射频感应加热的影响。采用G32线圈设计和三种人体解剖模型（杜克模型、埃拉模型和脂肪模型）对MRI射频线圈和患者进行建模。
患者、装置和线圈的相对位置会显著影响射频感应加热。在其他条件不变的情况下，改变装置位置或患者体位可导致1-g平均空间吸收率峰值变化约四倍。通过改变体表标志位置和患者体位，对于所研究的特定扫描情况，射频感应加热可从1323.6W/kg降至217.5W/kg。
患者体位、体表标志位置和装置位置会影响1.5T和3T时模块化外固定装置的射频感应加热。这些特性可用于在MRI期间简单实用地减少射频感应加热。
