title: An implantable RF solenoid for magnetic resonance microscopy and microspectroscopy.
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.
authors.affiliation: Department of Neurophysics, Max Planck Institute,Leipzig, Germany. dsrivera@ieee.org
authors.forename: D S
authors.initials: DS
authors.lastname: Rivera
authors.forename: M S
authors.initials: MS
authors.lastname: Cohen
authors.forename: W G
authors.initials: WG
authors.lastname: Clark
authors.forename: A C
authors.initials: AC
authors.lastname: Chu
authors.forename: R L
authors.initials: RL
authors.lastname: Nunnally
authors.forename: J
authors.initials: J
authors.lastname: Smith
authors.forename: D
authors.initials: D
authors.lastname: Mills
authors.forename: J W
authors.initials: JW
authors.lastname: Judy
mesh_terms: D017097:Electric Impedance; D004567:Electrodes, Implanted; D004867:Equipment Design; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008839:Microelectrodes; D008853:Microscopy / Q000295:instrumentation*; D008954:Models, Biological; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio