title: Accuracy of real-time MR temperature mapping in the brain: a comparison of fast sequences.
abstract: OBJECTIVE
  To compare magnetic resonance (MR) thermometry based on the proton resonance frequency (PRF) method using a single shot echoplanar imaging (ss EPI) sequence to both of the standard sequences, gradient echo (GRE) and segmented echoplanar imaging (seg EPI) in the in vivo human brain, at 1.5T and 3T.
  
  
  METHODS
  Repetitive MR thermometry was performed on the brain of six volunteers using GRE, seg EPI, and ss EPI sequences on whole-body 1.5T and 3T clinical systems using comparable acquisition parameters. Phase stability and temperature data precision in the human head were determined over 12 min for the three sequences at both field strengths. An ex-vivo swine skeletal muscle model was used to evaluate temperature accuracy of the ss EPI sequence during heating by high intensity focused ultrasound (HIFU).
  
  
  RESULTS
  In-vivo examinations of brain revealed an average temperature precision of 0.37 °C/0.39 °C/0.16 °C at 3T for the GRE/seg EPI/ss EPI sequences. At 1.5T, a precision of 0.58 °C/0.63 °C/0.21 °C was achieved. In the ex-vivo swine model, a strong correlation of temperature data derived using ss EPI and GRE sequences was found with a temperature deviation <1 °C.
  
  
  CONCLUSIONS
  The ss EPI sequence was the fastest and the most precise sequence for MR thermometry, with significantly higher accuracy compared to GRE.
authors.affiliation: Siemens Healthcare, H IM MR PLM AW Oncology, FH5/2008, Allee am Röthelheimpark 2, 91052 Erlangen, Germany. antje.kickhefel.ext@siemens.com
authors.forename: A
authors.initials: A
authors.lastname: Kickhefel
authors.forename: Jörg
authors.initials: J
authors.lastname: Roland
authors.forename: Clifford
authors.initials: C
authors.lastname: Weiss
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
mesh_terms: D000328:Adult; D001921:Brain; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011522:Protons; D013696:Temperature; D013821:Thermometers; D013997:Time Factors; D051598:Whole Body Imaging
chemical_list: D011522:Protons