title: MR temperature monitoring applying the proton resonance frequency method in liver and kidney at 0.2 and 1.5 T: segment-specific attainable precision and breathing influence.
abstract: OBJECTIVE
  The objective of this study was to evaluate breathing influence on precision in temperature determination by using the proton resonance frequency (PRF) shift method depending on the location in abdominal organs at 0.2 and 1.5 T.
  
  
  METHODS
  Phase images were acquired with gradient echo sequences in a total of 12 volunteers at 1.5 and 0.2 T. Different examination protocols were performed (each 8 measurements with (1) in-/expiration, (2) free breathing, (3) under breathhold, (4) with breathing belt triggering, and (5) with navigator triggering (integrated in MR signal acquisition). Regions of interest were placed on liver and kidneys, and the resulting phase differences between the measurements were transformed into corresponding temperature differences.
  
  
  RESULTS
  Precision significantly varied depending on the liver segment or location in the kidney. Gating techniques were found better than breathhold techniques and clearly better than non-gated examinations. The most precise approach reached a standard deviation of 2.0 degrees C under continuous breathing when navigator gating was used at 1.5 T.
  
  
  CONCLUSIONS
  PRF temperature measurement is feasible even for moving organs in the abdomen at 0.2 and 1.5 T. The location of the target region and the required precision of the measurements should direct the choice of examination mode.
authors.affiliation: Diagnostic and Interventional Radiology, University Hospital of Tübingen, Tübingen, Germany. hansjoerg.rempp@med.uni.tuebingen.de
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Rempp
authors.forename: Petros
authors.initials: P
authors.lastname: Martirosian
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
authors.forename: Stephan
authors.initials: S
authors.lastname: Clasen
authors.forename: Antje
authors.initials: A
authors.lastname: Kickhefel
authors.forename: Markus
authors.initials: M
authors.lastname: Kraiger
authors.forename: Christina
authors.initials: C
authors.lastname: Schraml
authors.forename: Claus
authors.initials: C
authors.lastname: Claussen
authors.forename: Philippe
authors.initials: P
authors.lastname: Pereira
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick