Reduction of Implant RF Heating Through Modification of Transmit Coil Electric Field
Reduction of Implant RF Heating Through Modification of Transmit Coil Electric Field
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DOI：
10.1002/mrm.22724
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发表时间：
2011-05-01
影响因子：
3.3
通讯作者：
Atalar, Ergin
中科院分区：
文献类型：
--
作者：
Eryaman, Yigitcan;Akin, Burak;Atalar, Ergin
在这项工作中，我们证明了修改射频（RF）线圈的电场分布以在体内产生无电场区而不显著改变发射灵敏度的可能性。由于植入物加热与电场分布直接相关，因此可以通过这种方法获得植入物友好的RF发射线圈。我们提出了一个线性鸟笼发射线圈与零电场平面作为这样的植入物友好线圈的一个例子。当零电场平面与植入物位置重合时，植入物加热减少，正如我们通过体模实验所证明的那样。通过向线圈的两个正交端口馈送具有相同相位和形状但不同振幅的RF脉冲，还可以调整零电场平面的位置。虽然这种方法可以减少植入物加热，但线性鸟笼线圈的全体积平均比吸收率是正交鸟笼线圈的两倍。为了解决这个问题，我们提出了替代方法来设计具有优化的电磁场和降低的全体积平均比吸收率的植入友好型RF线圈。通过这些方法，修改了发射场，以减少植入物的RF加热并获得均匀的发射灵敏度。Magn Reson Med 65：1305- 1313，2011. (c)2010 Wiley-Liss，Inc.
In this work, we demonstrate the possibility to modify the electric-field distribution of a radio frequency (RF) coil to generate electric field-free zones in the body without significantly altering the transmit sensitivity. Because implant heating is directly related to the electric-field distribution, implant-friendly RF transmit coils can be obtained by this approach. We propose a linear birdcage transmit coil with a zero electric-field plane as an example of such implant-friendly coils. When the zero electric-field plane coincides with the implant position, implant heating is reduced, as we demonstrated by the phantom experiments. By feeding RF pulses with identical phases and shapes but different amplitudes to the two orthogonal ports of the coil, the position of the zero electric-field plane can also be adjusted. Although implant heating is reduced with this method, a linear birdcage coil results in a whole-volume average specific absorption rate that is twice that of a quadrature birdcage coil. To solve this issue, we propose alternative methods to design implant-friendly RF coils with optimized electromagnetic fields and reduced whole-volume average specific absorption rate. With these methods, the transmit field was modified to reduce RF heating of implants and obtain uniform transmit sensitivity. Magn Reson Med 65:1305-1313,2011. (c) 2010 Wiley-Liss, Inc.