MR-based temperature monitoring for hot saline injection therapy

We applied magnetic resonance (MR) phase mapping methods to monitor the thermal frequency shift of water in order to study temperature changes from percutaneous hot saline injection therapy (PSIT) using in vitro swine livers and in vivo rabbit livers. The thermal coefficients calculated from the shifts of the water frequency with thermocouple based temperature measurements were -0.0085 ± 0.0019 ppm/°C for the in vitro studies and -0.0089 ppm/°C for the in vivo studies. The error range was estimated to be ± 3°C and ± 4.5 °C, respectively. Color-coded temperature maps were compared with macroscopic lesion sizes of the specimen. Regions defined using a 20°C elevation in the initial images following hot saline injection (around 55°C in absolute temperature) closely correlated with visible coagulation in size. We conclude that MR temperature monitoring of PSIT is quite feasible and may be helpful in expanding the clinical use of this thermal therapeutic tool for liver tumors. (C) 2000 Wiley-Liss, Inc.