title: In vivo radiofrequency heating in swine in a 3T (123.2-MHz) birdcage whole body coil.
abstract: OBJECTIVE
  To study in vivo radiofrequency (RF) heating produced due to power deposition from a 3T (Larmour frequency = 123.2 MHz), birdcage, whole body coil.
  
  
  METHODS
  The RF heating was simulated in a digital swine by solving the mechanistic generic bioheat transfer model (GBHTM) and the conventional, empirical Pennes bioheat transfer equation for two cases: 1) when the swine head was in the isocenter and 2) when the swine trunk was in the isocenter. The simulation results were validated by making direct fluoroptic temperature measurements in the skin, brain, simulated hot regions, and rectum of 10 swine (case 1: n = 5, mean animal weight = 84.03 ± 6.85 kg, whole body average SAR = 2.65 ± 0.22 W/kg; case 2: n = 5, mean animal weight = 81.59 ± 6.23 kg, whole body average SAR = 2.77 ± 0.26 W/kg) during 1 h of exposure to a turbo spin echo sequence.
  
  
  RESULTS
  The GBHTM simulated the RF heating more accurately compared with the Pennes equation. In vivo temperatures exceeded safe temperature thresholds with allowable SAR exposures. Hot regions may be produced deep inside the body, away from the skin.
  
  
  CONCLUSIONS
  SAR exposures that produce safe temperature thresholds need reinvestigation.
authors.affiliation: Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Devashish
authors.initials: D
authors.lastname: Shrivastava
authors.forename: Lynn
authors.initials: L
authors.lastname: Utecht
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Tian
authors.forename: John
authors.initials: J
authors.lastname: Hughes
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Vaughan
mesh_terms: D065638:Absorption, Radiation; D000818:Animals; D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006361:Heating / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008954:Models, Biological; D011829:Radiation Dosage; D011846:Radio Waves; D013552:Swine; D051598:Whole Body Imaging / Q000295:instrumentation / Q000379:methods*; D014916:Whole-Body Irradiation / Q000295:instrumentation / Q000379:methods*
keywords: 3T; MRI; bioheat; heating; safety