Temperature monitoring of focused ultrasound therapy by MRI

The aim of the present study was to assess the feasibility of MRI monitoring the temperature distribution induced by focused ultrasound therapy of malignant tissue in vivo. Male Copenhagen rats bearing R3327-AT1 Dunning prostate tumors were sonicated in vivo with a self-constructed CW-ultrasound source. The sonication was performed in a conventional 1.5 T whole-body MR scanner. For MRI a T1-weighted saturation recovery TurboFLASH (SRTF) sequence (TR=10.2 ms, TE=4 ms, TI=300 ms, α=12°) with an acquisition time of 1.3 s per image was used. After sonication hypo-intense regions inside the tumors were monitored expanding centripetally off the focus by time. Tumor growth delay and postmortem histology correlated with the temperature distributions calculated from the SRTF signals. This will temperature to be controlled interactively during US hyperthermia