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

Object: 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.

Materials and 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.

Conclusion: 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.