title: Thermal effects of focused ultrasound on the brain: determination with MR imaging.
abstract: OBJECTIVE
  To determine the feasibility of the use of temperature-sensitive magnetic resonance (MR) imaging for the detection of local temperature elevations at the focus of a low-power ultrasound beam in the brain.
  
  
  METHODS
  The brains in 28 rabbits were sonicated at acoustic power levels of 3.5-17.5 W. Four to five different locations were sonicated at different acoustic power levels in each rabbit. MR images were obtained 2 hours, 48 hours, 10 days, and 23 days after the sonications, depending on when the animals were sacrificed. Histologic evaluation of whole brain was performed.
  
  
  RESULTS
  Forty of 43 (93%) of the lowest-power (3.5-W) sonications were visible on temperature-sensitive MR images and did not result in any short- or long-term histologic or MR imaging evidence of tissue damage. A contrast-to-noise ratio of approximately 6 and a temperature elevation of 7 degrees-8 degrees C were observed.
  
  
  CONCLUSIONS
  Temperature elevations induced by means of focused ultrasound exposures that do not cause damage in the in vivo rabbit brain can be detected at temperature-sensitive MR imaging.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: K
authors.initials: K
authors.lastname: Hynynen
authors.forename: N I
authors.initials: NI
authors.lastname: Vykhodtseva
authors.forename: A H
authors.initials: AH
authors.lastname: Chung
authors.forename: V
authors.initials: V
authors.lastname: Sorrentino
authors.forename: V
authors.initials: V
authors.lastname: Colucci
authors.forename: F A
authors.initials: FA
authors.lastname: Jolesz
mesh_terms: D000818:Animals; D001706:Biopsy; D001831:Body Temperature; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D004195:Disease Models, Animal; D005240:Feasibility Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008991:Monitoring, Physiologic; D011817:Rabbits; D013997:Time Factors; D014464:Ultrasonic Therapy / Q000379:methods*; D018084:Ultrasonography, Interventional / Q000379:methods*