Study of laser ablation in the in vivo rabbit brain with MR thermometry

Purpose: To investigate the peak temperature and thermal dose (T₄₃) as tissue damage indicators for thermal therapy. Materials and Methods: The proton resonant frequency (PRF) shift thermal coefficient was calibrated on six in vivo rabbit brains during interstitial laser ablation. The peak temperature and T₄₃ were correlated with the lesion boundary observed on T2-weighted spin-echo (SE) MRI at 4 hours post-heating in seven thermal lesions using direct MR measurement and analysis based on a binary discriminate model. Results: The peak temperature and T₄₃ were 48.3 ± 1.7°C and 191 ± 219 minutes, respectively, from the direct MR measurement. The values derived by the binary discriminate analysis were 47.8 ± 2.2°C and 28 ± 41 minutes, respectively. Conclusion: Our results suggest that tissue damage in rabbit brain 4 hours after thermal ablation can be predicted reliably from a threshold temperature of approximately 48°C.