Magnetic Thin Film Shieldings on Electrical Wires
Date
2003
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Publisher
Alfred University. Faculty of Ceramic Engineering. Kazuo Inamori School of Engineering
Abstract
Magnetic Resonance Imaging (MRI) is a well-established diagnostic technique in clinical medicine. However, many patients with implanted medical devices cannot benefit from such an important diagnostic tool; the major reason for this is electromagnetic interference. The principle bio-effect is heating in the electrical wires of the implanted medical devices. One way to solve this problem is to shield the electrical wires from the magnetic field of MRI. This study focuses on determining the shielding effects of a thin film coated aluminum rod that simulates an electrical wire of implanted medical devices, such as cardiac pacemakers and spinal cord stimulators. A multi-layer thin film is coated onto the surface of the electrical wire. Experimentally, several different kinds of thin films, including aluminum nitride and aluminum iron, are deposited either on the silicon wafer or the aluminum rod by a sputtering deposition technique. Then several critical shielding properties of the asdeposited films are characterized using different methods. The heating effects are related to power loss induced by the RF magnetic field of MRI. Magnetic flux density and power loss are used as the parameters for shielding effect comparison. Computer simulations are performed to examine how the magnetic flux density and power loss are affected by the shell thickness, conductivity, and permeability. Temperature increases in the wire without shielding and with shielding is calculated from the simulation results of power loss. Therefore, optimal thin film shielding parameters are suggested to keep the heating effects in the wire at acceptable levels.
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Keywords
Shieldings, Electric current, Thin films, Wires, Magnetic properties