NT-32 * TISSUE ABLATION DYNAMICS DURING MAGNETIC RESONANCE-GUIDED LASER INDUCED THERMAL THERAPY FOR INTRACRANIAL TUMORS

Abstract

BACKGROUND: Magnetic Resonance-guided Laser Induced Thermal Therapy (MRgLITT) is a minimally-invasive procedure used in the treatment of intracranial tumors, epilepsy and pain. Thermal damage is estimated using real-time MR thermometry but little is known about the dynamics of the process and how various intracranial tumors affect overall ablation. OBJECTIVES: Determine the relationship between thermal energy delivery and the time to maximal estimated thermal damage in the setting of previously untreated glioblastoma multiforme (GBM), recurrent GBM, and metastatic tumors or radiation necrosis. We aim to understand whether differences exist between these intracranial malignancies and how the ablation process is affected. METHODS: We used real-time ablation data from 24 patients across five unique intracranial pathologies. Ablations were performed using the Visualase Thermal Therapy System (Visulase Inc.) using a 980-nm diffusing tip diode laser. Thermal damage area was plotted against time for each ablation. Subsequently, the duration required to reach 50% (t50) and 97% (t97) of maximum damage was estimated. Comparisons were then made between different intracranial pathologies. RESULTS: The average (mean ± SEM) t97 for previously untreated GBM (n = 7) recurrent GBM (n = 6) and tumor metastasis/radiation necrosis (n = 7) are 167 ± 18, 165 ± 22, 97 ± 22 seconds, respectively. The mean t97 is significantly shorter for tumor metastasis/radiation necrosis when compared with previously untreated GBM (p < 0.05). CONCLUSIONS: While optimal duration of thermal ablation varies between intracranial tumors, we found that metastatic tumor/radiation necrosis requires significantly shorter duration of ablation. In most cases, maximal ablation was reached long before the industry recommended ablation time. Understanding the duration required to reach maximal ablation may reduce thermal exposure times during the ablation process. Future studies are needed to examine the relationship between ablation power, irrigation speed, and the effect of prior therapies on the ablation dynamics.