深部脑刺激电极的磁共振成像相关加热：体外研究
MR imaging-related heating of deep brain stimulation electrodes: in vitro study.
作者信息
Finelli Daniel A, Rezai Ali R, Ruggieri Paul M, Tkach Jean A, Nyenhuis John A, Hrdlicka Greg, Sharan Ashwini, Gonzalez-Martinez Jorge, Stypulkowski Paul H, Shellock Frank G
机构信息
Division of Radiology, Section of Stereotactic and Functional Neurosurgery, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
出版信息
AJNR Am J Neuroradiol. 2002 Nov-Dec;23(10):1795-802.
BACKGROUND AND PURPOSE
Recent work has shown a potential for excessive heating of deep brain stimulation electrodes during MR imaging. This in vitro study investigates the relationship between electrode heating and the specific absorption rate (SAR) of several MR images.
METHODS
In vitro testing was performed by using a 1.5-T MR imaging system and a head transmit-receive coil, with bilateral deep brain stimulation systems positioned in a gel saline-filled phantom, and temperature monitoring with a fluoroptic thermometry system. Standardized fast spin-echo sequences were performed over a range of high, medium, and low SAR values. Several additional, clinically important MR imaging techniques, including 3D magnetization prepared rapid acquisition gradient-echo imaging, echo-planar imaging, quantitative magnetization transfer imaging, and magnetization transfer-suppressed MR angiography, were also tested by using typical parameters.
RESULTS
A significant, highly linear relationship between SAR and electrode heating was found, with the temperature elevation being approximately 0.9 times the local SAR value. Minor temperature elevations, <1 degrees C, were found with the fast spin-echo, magnetization prepared rapid acquisition gradient-echo, and echo-planar clinical imaging sequences. The high dB/dt echo-planar imaging sequence had no significant heating independent of SAR considerations. Sequences with magnetization transfer pulses produced temperature elevations in the 1.0 to 2.0 degrees C range, which was less than theoretically predicted for the relatively high SAR values.
CONCLUSION
A potential exists for excessive MR imaging-related heating in patients with deep brain stimulation electrodes; however, the temperature increases are linearly related to SAR values. Clinical imaging sequences that are associated with tolerable temperature elevations in the <or=2.0 degrees C range at the electrode tips can be performed safely within an SAR range <2.4 W/kg local (0.9 W/kg whole body averaged).
背景与目的
近期研究表明，在磁共振成像（MR成像）过程中，深部脑刺激电极存在过热的可能性。本体外研究旨在探究电极发热与几种MR图像的比吸收率（SAR）之间的关系。
方法
使用1.5-T MR成像系统和头部发射-接收线圈进行体外测试，将双侧深部脑刺激系统置于充满凝胶盐水的体模中，并使用荧光光学测温系统监测温度。在一系列高、中、低SAR值范围内执行标准化快速自旋回波序列。还使用典型参数测试了其他几种具有临床重要性的MR成像技术，包括三维磁化准备快速采集梯度回波成像、回波平面成像、定量磁化传递成像以及磁化传递抑制磁共振血管造影。
结果
发现SAR与电极发热之间存在显著的高度线性关系，温度升高约为局部SAR值的0.9倍。在快速自旋回波、磁化准备快速采集梯度回波和回波平面临床成像序列中发现温度有轻微升高，<1℃。高dB/dt回波平面成像序列在不考虑SAR的情况下没有明显发热。带有磁化传递脉冲的序列产生的温度升高在1.0至2.0℃范围内，低于相对较高SAR值的理论预测值。
结论
深部脑刺激电极患者存在与MR成像相关的过度发热风险；然而，温度升高与SAR值呈线性相关。在电极尖端温度升高≤2.0℃范围内可耐受的临床成像序列，可在局部SAR<2.4 W/kg（全身平均0.9 W/kg）的范围内安全进行。
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