An implantable RF solenoid for magnetic resonance microscopy and microspectroscopy

IEEE Trans Biomed Eng. 2012 Aug;59(8):2118-25. doi: 10.1109/TBME.2011.2178239. Epub 2011 Dec 6.

Abstract

Miniature solenoids routinely enhance small volume nuclear magnetic resonance imaging and spectroscopy; however, no such techniques exist for patients. We present an implantable microcoil for diverse clinical applications, with a microliter coil volume. The design is loosely based on implantable depth electrodes, in which a flexible tube serves as the substrate, and a metal stylet is inserted into the tube during implantation. The goal is to provide enhanced signal-to-noise ratio (SNR) of structures that are not easily accessed by surface coils. The first-generation prototype was designed for implantation up to 2 cm, and provided initial proof-of-concept for microscopy. Subsequently, we optimized the design to minimize the influence of lead inductances, and to thereby double the length of the implantable depth (4 cm). The second-generation design represents an estimated SNR improvement of over 30% as compared to the original design when extended to 4 cm. Impedance measurements indicate that the device is stable for up to 24 h in body temperature saline. We evaluated the SNR and MR-related heating of the device at 3T. The implantable microcoil can differentiate fat and water peaks, and resolve submillimeter features.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Electric Impedance
  • Electrodes, Implanted*
  • Equipment Design
  • Humans
  • Magnetic Resonance Imaging / instrumentation*
  • Microelectrodes
  • Microscopy / instrumentation*
  • Models, Biological
  • Phantoms, Imaging
  • Signal-To-Noise Ratio