用于介入性神经血管磁共振成像的基于同轴传输线谐振器的导管射频线圈设计
Design of catheter radio frequency coils using coaxial transmission line resonators for interventional neurovascular MR imaging.
作者信息
Zhang Xiaoliang, Martin Alastair, Jordan Caroline, Lillaney Prasheel, Losey Aaron, Pang Yong, Hu Jeffrey, Wilson Mark, Cooke Daniel, Hetts Steven W
机构信息
Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
UC Berkeley/UCSF Joint Bioengineering Program, University of California, Berkeley, San Francisco, CA, USA.
出版信息
Quant Imaging Med Surg. 2017 Apr;7(2):187-194. doi: 10.21037/qims.2016.12.05.
BACKGROUND
It is technically challenging to design compact yet sensitive miniature catheter radio frequency (RF) coils for endovascular interventional MR imaging.
METHODS
In this work, a new design method for catheter RF coils is proposed based on the coaxial transmission line resonator (TLR) technique. Due to its distributed circuit, the TLR catheter coil does not need any lumped capacitors to support its resonance, which simplifies the practical design and construction and provides a straightforward technique for designing miniature catheter-mounted imaging coils that are appropriate for interventional neurovascular procedures. The outer conductor of the TLR serves as an RF shield, which prevents electromagnetic energy loss, and improves coil Q factors. It also minimizes interaction with surrounding tissues and signal losses along the catheter coil. To investigate the technique, a prototype catheter coil was built using the proposed coaxial TLR technique and evaluated with standard RF testing and measurement methods and MR imaging experiments. Numerical simulation was carried out to assess the RF electromagnetic field behavior of the proposed TLR catheter coil and the conventional lumped-element catheter coil.
RESULTS
The proposed TLR catheter coil was successfully tuned to 64 MHz for proton imaging at 1.5 T. B fields were numerically calculated, showing improved magnetic field intensity of the TLR catheter coil over the conventional lumped-element catheter coil. MR images were acquired from a dedicated vascular phantom using the TLR catheter coil and also the system body coil. The TLR catheter coil is able to provide a significant signal-to-noise ratio (SNR) increase (a factor of 200 to 300) over its imaging volume relative to the body coil.
CONCLUSIONS
Catheter imaging RF coil design using the proposed coaxial TLR technique is feasible and advantageous in endovascular interventional MR imaging applications.
背景
设计用于血管内介入磁共振成像的紧凑且灵敏的微型导管射频（RF）线圈在技术上具有挑战性。
方法
在这项工作中，基于同轴传输线谐振器（TLR）技术提出了一种新的导管RF线圈设计方法。由于其分布式电路，TLR导管线圈不需要任何集总电容来支持其谐振，这简化了实际设计和构建，并为设计适用于介入性神经血管手术的微型导管安装成像线圈提供了一种直接的技术。TLR的外导体用作RF屏蔽，可防止电磁能量损失，并提高线圈品质因数。它还可最大程度减少与周围组织的相互作用以及沿导管线圈的信号损失。为了研究该技术，使用所提出的同轴TLR技术构建了一个原型导管线圈，并通过标准RF测试和测量方法以及MR成像实验进行了评估。进行了数值模拟，以评估所提出的TLR导管线圈和传统集总元件导管线圈的RF电磁场行为。
结果
所提出的TLR导管线圈成功调谐至64 MHz用于1.5 T的质子成像。通过数值计算得出了B场，结果表明TLR导管线圈的磁场强度优于传统集总元件导管线圈。使用TLR导管线圈以及系统体线圈从专用血管模型获取了MR图像。相对于体线圈，TLR导管线圈在其成像体积上能够显著提高信噪比（SNR）（提高200至300倍）。
结论
使用所提出的同轴TLR技术进行导管成像RF线圈设计在血管内介入MR成像应用中是可行且具有优势的。
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