Real-time monitoring of radiofrequency ablation of rabbit liver by respiratory-gated quantitative temperature MRI.

PURPOSE: To evaluate the feasibility and precision of magnetic resonance imaging (MRI) thermometry for monitoring radiofrequency (RF) liver ablation in vivo and predicting the size of the ablation zone.

MATERIALS AND METHODS: At 1.5T, respiratory-triggered real-time MR temperature mapping (the proton resonance frequency (PRF) method) was used to monitor RF ablation in rabbit liver (N = 6) under free breathing. The size of the ablation zones, as assessed by histological analyses, was compared with that predicted from MR thermal dose (TD) maps or derived from conventional T1-weighted (T1w), T2-weighted (T2w), and T1w gadolinium (Gd)-enhanced (T1w-Gd) images acquired immediately after the ablation, and on days 4 and 8 postprocedure.

RESULTS: MR temperature uncertainty remained under 1-2 degrees C even during RF deposition. The TD maps were shown to be more predictive and precise than the other MR images, with an average predictive precision for the final ablation zone size of about 1 mm as compared to the histologically proven lesion on day 8.

CONCLUSION: Quantitative temperature MRI during RF ablation is feasible and offered a precise indication of the ablation zone size in this preclinical study based on the lethal dose threshold.