Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous model
Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous model
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DOI：
10.1002/mrm.26622
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发表时间：
2017-12-01
影响因子：
3.3
通讯作者：
Graham, Simon J.
中科院分区：
文献类型：
--
作者：
McElcheran, Clare E.;Yang, Benson;Graham, Simon J.
目的细长的植入导体可以在 MRI 期间与射频 (RF) 传输场相互作用，从而给使用深部脑刺激器的患者带来过度加热的安全问题。在具有双边和单边弯曲导线的拟人异质模型上评估使用并行射频传输 (pTx) 的技术。方法通过仿真优化幅度和相位，以最大限度地减少植入导线周围的热量，并最大限度地减少异质模型中四通道和八通道 pTx 的 B1+ 不均匀性。 MRI 实验是在从通用数字网格文件创建的等效测试体模中进行的。结果在四通道 pTx 中，单侧和双侧导线的最大局部比吸收率 (SAR) 分别降低了 47% 和 59%，但 B1+ 均匀性受损。与单侧和双边导线中的鸟笼线圈射频激励相比，优化的八通道 pTx 显着降低了局部 SAR（最大局部 SAR 分别降低了 79% 和 87%）。 B1+ 不均匀性分别限制在 17% 和 26%。四通道 pTx 的实验验证显示，导线 1 和导线 2 的尖端温度分别降低了 80% 和 92%。结论 这种 pTx 方法有望降低单侧和双边植入导线尖端的局部 SAR，同时保持模拟和实验中的图像质量。 Magn Reson Med 78:2408-2415, 2017。(c) 2017 年国际医学磁共振学会。
PurposeElongated implanted conductors can interact with the radiofrequency (RF) transmission field during MRI, posing safety concerns of excessive heating in patients with deep brain stimulators. A technique using parallel RF transmission (pTx) is evaluated on an anthropomorphic heterogeneous model with bilateral and unilateral curved wires.MethodsAmplitude and phase were optimized by simulation to minimize heating surrounding the implanted wires and to minimize B1+ inhomogeneity for four-channel and eight-channel pTx in a heterogeneous model. MRI experiments were conducted in an equivalent test phantom created from a common digital mesh file.ResultsIn four-channel pTx, maximum local specific absorption rate (SAR) was reduced in both unilateral and bilateral wires by 47% and 59%, respectively, but with compromised B1+ homogeneity. Optimized eight-channel pTx substantially reduced local SAR compared with birdcage coil RF excitation in both unilateral and bilateral wires (reduction of maximum local SAR of 79% and 87%, respectively). B1+ inhomogeneity was limited to 17% and 26%, respectively. Experimental validation with four-channel pTx showed 80% and 92% temperature reduction at the tips of wire 1 and wire 2, respectively.ConclusionThis pTx approach yields promising reductions in local SAR at the tips of unilateral and bilateral implanted wires while maintaining image quality in simulation and experiment. Magn Reson Med 78:2408-2415, 2017. (c) 2017 International Society for Magnetic Resonance in Medicine.