title: Radiofrequency heating in porcine models with a "large" 32 cm internal diameter, 7 T (296 MHz) head coil.
abstract: Temperatures were measured in vivo in four pigs (mean animal weight = 110.75 kg and standard deviation = 6.13 kg) due to a continuous wave radiofrequency (RF) power irradiation with a 31.75 cm internal diameter and a 15.24 cm long, 7 T (296 MHz), eight channel, transverse electromagnetic head coil. The temperatures were measured in the subcutaneous layer of the scalp, 5, 10, 15, and 20 mm deep in the brain, and rectum using fluoroptic temperature probes. The RF power was delivered to the pig's head for ∼3 h (mean deposition time = 3.14 h and standard deviation = 0.06 h) at the whole head average specific absorption rate of ∼3 W kg(-1) (mean average specific absorption rate = 3.08 W kg(-1) and standard deviation = 0.09 W kg(-1)). Next, simple bioheat transfer models were used to simulate the RF power induced temperature changes. Results show that the RF power produced uniform temperature changes in the pigs' heads (mean temperature change = 1.68°C and standard deviation = 0.13°C) with no plateau achieved during the heating. No thermoregulatory alterations were detected due to the heating because the temperature responses of the pre-RF and post-RF epochs were not statistically significantly different. Simple, validated bioheat models may provide accurate temperature changes.
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota 55455, USA. dev@cmrr.umn.edu
authors.forename: Devashish
authors.initials: D
authors.lastname: Shrivastava
authors.forename: Timothy
authors.initials: T
authors.lastname: Hanson
authors.forename: Jeramy
authors.initials: J
authors.lastname: Kulesa
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Tian
authors.forename: Gregor
authors.initials: G
authors.lastname: Adriany
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Vaughan
mesh_terms: D000818:Animals; D001921:Brain / Q000528:radiation effects*; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D023421:Models, Animal; D011846:Radio Waves; D012449:Safety; D013552:Swine