title: Ensuring safety of implanted devices under MRI using reversed RF polarization.
abstract: Patients with long-wire medical implants are currently prevented from undergoing magnetic resonance imaging (MRI) scans due to the risk of radio frequency (RF) heating. We have developed a simple technique for determining the heating potential for these implants using reversed radio frequency (RF) polarization. This technique could be used on a patient-to-patient basis as a part of the standard prescan procedure to ensure that the subject's device does not pose a heating risk. By using reversed quadrature polarization, the MR scan can be sensitized exclusively to the potentially dangerous currents in the device. Here, we derive the physical principles governing the technique and explore the primary sources of inaccuracy. These principles are verified through finite-difference simulations and through phantom scans of implant leads. These studies demonstrate the potential of the technique for sensitively detecting potentially dangerous coupling conditions before they can do any harm.
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305-9510, USA. wro@stanford.edu
authors.forename: William R
authors.initials: WR
authors.lastname: Overall
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.forename: Pascal P
authors.initials: PP
authors.lastname: Stang
authors.forename: Greig C
authors.initials: GC
authors.lastname: Scott
mesh_terms: D000465:Algorithms; D002058:Burns, Electric / Q000209:etiology* / Q000517:prevention & control*; D017076:Computer-Aided Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects* / Q000295:instrumentation*; D019736:Prostheses and Implants / Q000009:adverse effects*; D011846:Radio Waves