title: Ultrafast 1D MR thermometry using phase or frequency mapping.
abstract: OBJECTIVE
  To develop an ultrafast MRI-based temperature monitoring method for application during rapid ultrasound exposures in moving organs.
  
  
  METHODS
  A slice selective 90° - 180° pair of RF pulses was used to solicit an echo from a column, which was then sampled with a train of gradient echoes. In a gel phantom, phase changes of each echo were compared to standard gradient-echo thermometry, and temperature monitoring was tested during focused ultrasound sonications. Signal-to-noise ratio (SNR) performance was evaluated in vivo in a rabbit brain, and feasibility was tested in a human heart.
  
  
  RESULTS
  The correlation between each echo in the acquisition and MRI-based temperature measurements was good (R = 0.98 ± 0.03). A temperature sampling rate of 19 Hz was achieved at 3T in the gel phantom. It was possible to acquire the water frequency in the beating heart muscle with 5-Hz sampling rate during a breath hold.
  
  
  CONCLUSIONS
  Ultrafast thermometry via phase or frequency monitoring along single columns was demonstrated. With a temporal resolution around 50 ms, it may be possible to monitor focal heating produced by short ultrasound pulses.
authors.affiliation: Department of Physics, Boston College, Chestnut Hill, MA, USA. meic@bwh.harvard.edu
authors.forename: Chang-Sheng
authors.initials: CS
authors.lastname: Mei
authors.forename: Robert V
authors.initials: RV
authors.lastname: Mulkern
authors.forename: Koichi
authors.initials: K
authors.lastname: Oshio
authors.forename: Nan-kuei
authors.initials: NK
authors.lastname: Chen
authors.forename: Bruno
authors.initials: B
authors.lastname: Madore
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: Panych
authors.forename: Kullervo
authors.initials: K
authors.lastname: Hynynen
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: McDannold
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D002138:Calibration; D004867:Equipment Design; D005782:Gels; D006321:Heart / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009068:Movement; D009206:Myocardium / Q000473:pathology; D019047:Phantoms, Imaging; D011522:Protons; D011817:Rabbits; D011846:Radio Waves; D059629:Signal-To-Noise Ratio; D013696:Temperature; D014465:Ultrasonics; D014867:Water / Q000737:chemistry
chemical_list: D005782:Gels; D011522:Protons; D014867:Water