EX-VIVO TISSUE-TYPE INDEPENDENCE IN PROTON-RESONANCE FREQUENCY-SHIFT MR THERMOMETRY

The temperature sensitivity of the proton-resonance frequency (PRF) ha s proven valuable for the monitoring of MR image-guided thermal coagul ation therapy. However, there is significant inconsistency in reported values of the PRF-thermal coefficient, as measured from experiments e ncompassing a range of in vivo and ex vivo tissue types and experiment al conditions. A method of calibrating the temperature dependence of t he PRF is described and results are presented that indicate a tissue-t ype independence. To this end, other possible mechanisms for variation s in the PRF-thermal coefficient are suggested, including physiologica l perturbations and volume magnetic susceptibility effects from geomet ry and orientation.