Towards a microcoil for intracranial and intraductal MR microscopy.
Towards a microcoil for intracranial and intraductal MR microscopy.
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用于颅内和导管内 MR 显微镜检查的微线圈。
DOI：
10.1109/iembs.2008.4649594
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Judy,JackW
中科院分区：
文献类型：
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作者：
Strick,DebraS;Nunnally,RayL;Smith,JolindaC;Clark,W;Mills,DixieJ;Cohen,MarkS;Judy,JackW
植入式射频线圈使深度结构的亚毫米分辨率磁共振成像（MRI）成为可能。缩小射频线圈的尺寸也同样提高了核磁共振光谱的信噪比。通过结合这两种方法，我们设计、制造并成像了一种植入式微线圈导管。虽然典型的植入式导管使用横向磁化，但微线圈的轴向磁化提供了更高的灵敏度，并允许可视化导管远端以外的组织。微线圈导管的直径为1mm，用于未来与颅内装置的整合，并用于乳腺肿瘤的导管内应用。我们修改了核磁共振微线圈的设计，通过将微线圈缠绕在医用级硅胶管上，并将导管上的引线连接电路元件，从而允许植入射频线圈。为了获得适当的匝距，我们在铜线上涂覆了25 μm的生物相容性聚合物（聚对二甲苯C）。调谐和匹配电路确保RF线圈的阻抗在3-T质子MR应用的工作频率下约为50 Ω。使用双工器使微线圈导管作为收发器使用。通过神经组织的离体成像实现了线圈设计的实验验证。正如预期的那样，微线圈导管提供了20 μm平面内分辨率和170 μm厚度的微尺度图像。虽然3-T MRI通常每立方毫米提供1到30个体素，但在本文中，我们报告了MRI微线圈可以在相同体积内提供数百甚至数千个体素。
Implantable RF-coils have enabled sub-mm resolution magnetic resonance images (MRI) of deep structures. Scaling down the size of RF coils has similarly provided a gain in signal-to-noise ratio in nuclear-magnetic-resonance spectroscopy. By combining both approaches we designed, fabricated, and imaged with an implantable microcoil catheter. While typical implantable catheters use a transverse magneti-zation, the axial magnetization of the microcoil provides improved sensitivity and allows visualization of the tissue beyond the distal end of the catheter. The microcoil catheter was designed with a diameter of 1 mm for future integration with intracranial devices, and for intraductal use in breast oncology. We modified the NMR-microcoil design to allow implantation of the RF coil, by winding the microcoil on medical-grade silicone tubing and incorporating leads on the catheter to connect circuit components. In order to achieve proper turn spacing, we coated copper wire with 25 μm of biocompatible polymer (Parylene C). Tuning and matching circuitry insured that the impedance of the RF coil was approximately 50 Ω at the operating frequency for 3-T proton MR applications. A duplexer was used to enable use of the microcoil catheter as a transceiver. Experimental verification of the coil design was achieved through ex vivo imaging of neural tissue. As expected, the microcoil catheter provided microscale images with 20-μm in-plane-resolution and 170-μm-thick slices. While 3-T MRI typically provides 1 to 30 voxels per-cubic-millimeter, in this paper we report that the MRI microcoil can provide hundreds, and even thousands of voxels in the same volume.