MRI‐guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: Demonstration of feasibility at 0.2 T

Successful radiofrequency (RF) thermal ablation was performed on VX2 tumors implanted in 23 rabbit livers under magnetic resonance (MR) guidance using a C‐arm‐shaped low‐field 0.2 T system. RF application and immediate postprocedure MRI of all animals was performed [T2‐weighted, turbo short tau inversion recovery (STIR), T1‐weighted before and after gadopentetate dimeglumine administration). Follow‐up MRI with a superparamagnetic iron oxide (SPIO) contrast medium was performed in nine rabbits at 2 weeks and in four rabbits at 1 month post RF ablation. All livers were harvested for pathologic examination. T2‐weighted and turbo‐STIR images demonstrated the highest tumor‐to‐RF‐thermal lesion contrast‐to‐noise ratios (CNRs; means 4.5 and 3.8, respectively) on postprocedure images; this was redemonstrated at 2‐ and 4‐week follow‐up imaging. T2‐weighted imaging never overestimated pathologic lesion size by more than 2 mm, and the radiologic‐pathologic correlation coefficient was not less than 0.90. In conclusion, MRI‐guided RF thermal ablation in implanted liver tumor is feasible using a C‐arm‐shaped low‐field 0.2 T system. The thermal lesion size can be most accurately monitored with T2‐weighted and turbo‐STIR images. Magn Reson Med 42:141–149, 1999. © 1999 Wiley‐Liss, Inc.