title: Radiofrequency heating effects around resonant lengths of wire in MRI.
abstract: Several recent reports agree that the potentially dangerous heating around extended wires or coaxial cables inside the bodycoil of a magnetic resonance imager is related to resonant effects. No quantitative description of this idea has been given so far. We analyse a simplified situation, where a straight metallic wire is completely surrounded by a large volume of homogeneous dielectric with a small conductivity. If it has the correct length, the wire acts as a receiving-and-retransmission antenna, changing the axial symmetry of the incoming electric field into a radially outgoing electric field near the wire ends. The latter field points into the conducting surroundings, causing dissipation. Some simple experiments on geometries related to this theoretical model provide support to the main conclusions. These suggest that under actual imaging conditions resonant effects might be avoided by choosing a wire length of about 2 m. However, more experimental work remains to be done to validate this suggestion.
authors.affiliation: Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Pictet
authors.forename: Reto
authors.initials: R
authors.lastname: Meuli
authors.forename: Stephan
authors.initials: S
authors.lastname: Wicky
authors.forename: Jacques J
authors.initials: JJ
authors.lastname: van der Klink
mesh_terms: D003198:Computer Simulation; D003300:Copper; D004553:Electric Conductivity; D004559:Electric Wiring; D004574:Electromagnetic Fields; D004869:Equipment Safety / Q000379:methods; D006358:Hot Temperature; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008962:Models, Theoretical; D011846:Radio Waves; D012680:Sensitivity and Specificity; D012965:Sodium Chloride; D013696:Temperature
chemical_list: D012965:Sodium Chloride; D003300:Copper