title: Temperature changes induced in human muscle by radio-frequency H-1 decoupling: measurement with an MR imaging diffusion technique. Work in progress.
abstract: To investigate temperature increases in tissues during magnetic resonance (MR) imaging or spectroscopy, the authors measured temperature changes in vitro and in vivo (leg of a volunteer) in a condition simulating hydrogen-1 decoupling in MR spectroscopy. Noninvasive measurements were obtained by using the temperature dependence of the translational diffusion coefficient of water. Temperature was measured at 0.5 T (86 MHz) by using a stimulated-echo sequence that included intense gradient pulses and a procedure reducing sensitivity to bulk tissue motion. Calibration curves of the diffusion coefficient against thermocouple-measured temperature were obtained for a gelatin phantom and bovine muscle. Temperature changes were 5.3 degrees C +/- 0.5 at 2.5 cm from the coil in gelatin and 7.7 degrees C +/- 0.5 at 0.7 cm in bovine muscle. The temperature changed by 4.9 degrees C +/- 1.9 at 2.2 cm from the coil in the calf muscle of a volunteer. The H-1 decoupling protocol can be adapted (modifications in transmission power, duty cycle) to reduce heating effects to below safety recommendations.
authors.affiliation: Service Hospitalier Frédéric Joliot, Orsay, France.
authors.forename: D
authors.initials: D
authors.lastname: Morvan
authors.forename: A
authors.initials: A
authors.lastname: Leroy-Willig
authors.forename: P
authors.initials: P
authors.lastname: Jehenson
authors.forename: C A
authors.initials: CA
authors.lastname: Cuenod
authors.forename: A
authors.initials: A
authors.lastname: Syrota
mesh_terms: D000818:Animals; D001831:Body Temperature; D002417:Cattle; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D009132:Muscles / Q000502:physiology*