Lin C, Bernstein M
IU School of Medicine, Indianapolis, IN.
Mayo Clinic, Rochester, MN.
Med Phys. 2012 Jun;39(6Part28):3975. doi: 10.1118/1.4736221.
To evaluate the difference in RF heating of deep brain stimulator (DBS) leads during MRI procedures using head-only transmitting coil versus whole-body transmitting coil.
A DBS lead was inserted into the center of a 3-liter head phantom constructed and filled with gel prepared according the specifications in ATSM standard 2182. The portion of the lead outside of the head phantom was either coiled and fixed to phantom exterior (lead only), similar to that in DBS implanting surgery, or connected through an extension cable to an IPG, which is set to zero mA output and turned off (lead+Ext.+IPG). Imaging was performed on a 1.5T MRI scanner using either a T/R head coil or the built-in T/R body coil. Two different scans: 3D MPRAGE (low SAR) and 3D TSE (high SAR) were performed. The temperature at the tip of the DBS lead was recorded every 10s using a fiber optical probe.
For lead only, the maximum temperature change (peak-to-peak) was less than 0.1 C with all scans or coils. For lead+Ext.+IPG, 0.4 C change was observed with T/R head coil and 0.95 C with T/R body coil for 3D MPRAGE (low SAR). However, 18.0 C and 35.3 C changes were observed, respectively, for 3D TSE (high SAR).
If the DBS lead is NOT connected to the IPG, no substantial difference in RF heating between the use of a T/R head coil and body coil transmit was observed. The temperature changes were minimal even under high SAR. Such results suggests that DBS MRI may be performed safely with transmitting through body coil and receiving through phased array surface coils provided ONLY the lead is present which is often the case during intra-operative procedures. Since further study is needed, extreme caution is advised before extrapolating these results to patient exams.
评估在磁共振成像（MRI）检查过程中，使用仅头部发射线圈与全身发射线圈时，深部脑刺激器（DBS）电极的射频加热差异。
将一根DBS电极插入一个3升的头部模型中心，该模型按照美国材料与试验协会（ASTM）标准2182的规格构建并填充凝胶。电极位于头部模型外部的部分要么盘绕并固定在模型外部（仅电极），类似于DBS植入手术中的情况，要么通过延长电缆连接到植入式脉冲发生器（IPG），将其设置为零毫安输出并关闭（电极+延长线+IPG）。使用T/R头部线圈或内置的T/R体线圈在1.5T MRI扫描仪上进行成像。进行两种不同的扫描：3D MPRAGE（低比吸收率）和3D TSE（高比吸收率）。使用光纤探头每10秒记录一次DBS电极尖端的温度。
对于仅电极的情况，所有扫描或线圈下的最大温度变化（峰峰值）均小于0.1℃。对于电极+延长线+IPG，在3D MPRAGE（低比吸收率）扫描中，使用T/R头部线圈时温度变化为0.4℃，使用T/R体线圈时为0.95℃。然而，在3D TSE（高比吸收率）扫描中，温度变化分别为18.0℃和35.3℃。
如果DBS电极未连接到IPG，则在使用T/R头部线圈和体线圈发射时，射频加热没有显著差异。即使在高比吸收率情况下，温度变化也很小。这些结果表明，只要电极存在（这在术中操作时通常是这样），通过体线圈发射并通过相控阵表面线圈接收来进行DBS MRI可能是安全的。由于需要进一步研究，在将这些结果外推到患者检查之前，建议极度谨慎。
