title: Heating of metallic rods induced by time-varying gradient fields in MRI.
abstract: OBJECTIVE
  To develop and validate an analytical technique to estimate the heating of metallic rods by magnetic resonance imaging (MRI) gradient fields to aid developers of MRI-compatible devices.
  
  
  METHODS
  Twelve rods (12.7 mm diameter, 127 mm long) were used. The magnetic field was provided by a custom-made water-cooled solenoid driven by a 1 kHz sinusoidal waveform with a 7.2 A peak current. The sample was insulated with polystyrene and the temperature measured using an MR-compatible thermocouple system (Sa1-E from Omega). Measurements were recorded using a National Instruments SCXI-1303. The AC/DC module of COMSOL 3.4 was used for finite element analysis of the power deposited.
  
  
  RESULTS
  Finite element analysis (FEA) showed good correspondence with the analytical estimates for the rod parallel to the field and then FEA was used to determine the scaling function for the rod perpendicular to the field. The experimental results showed good correlation with the theoretical estimate when the finite length of the test coil was accounted for.
  
  
  CONCLUSIONS
  A new scaling function for the rod perpendicular to the field was developed. Heating in this orientation is double that of the parallel case. The results will aid developers of MRI-compatible devices in estimating heating before testing in the MRI.
authors.affiliation: Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada.
authors.forename: Khaled
authors.initials: K
authors.lastname: El Bannan
authors.forename: William
authors.initials: W
authors.lastname: Handler
authors.forename: Blaine
authors.initials: B
authors.lastname: Chronik
authors.forename: Shaun P
authors.initials: SP
authors.lastname: Salisbury
mesh_terms: D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D004735:Energy Transfer / Q000528:radiation effects; D006361:Heating / Q000379:methods*; D006358:Hot Temperature; D008279:Magnetic Resonance Imaging; D008422:Materials Testing; D008670:Metals / Q000528:radiation effects*; D008962:Models, Theoretical; D011829:Radiation Dosage
chemical_list: D008670:Metals
keywords: MR safety; gradient switching; heating estimate