Neurosurgery 77:51–58, 2015
Magnetic resonance–guided, laser-induced thermal therapy is a real- time magnetic resonance thermometry–guided, minimally invasive procedure used in the treatment of intracranial tumors, epilepsy, and pain. Little is known about its dynamics and the effects of various pathologies on overall ablation.
OBJECTIVE: To determine the relationship between thermal energy delivery and the time to maximal estimares thermal damage and whether differences exist between various intracranial pathologies.
METHODS: We used real-time ablation data from 28 patients across 5 unique intra- cranial pathologies. All ablations were performed using the Visualase Thermal Therapy System (Medtronic, Inc, Minneapolis, Minnesota), which uses a 980-nm diffusing tip diode laser. The thermal damage area was plotted against time for each ablation. We then estimated the duration of time required to reach 50% (t 50 ) and 97% (t 97 ) of maximal damage. Comparisons were then made between different intracranial pathologies.
RESULTS: The duration required to reach maximal thermal damage estimate (TDE) among all ablations was 159+-2 seconds, and the t 50 and t 97 were 43 21 and 136+-57 seconds, respectively, where t 97 was reached at an average of 23 seconds before the maximal TDE. The t 97 was shorter in the recurrent metastasis/radiation necrosis and epilepsy groups compared with the previously untreated glioblastoma multiforme group.
CONCLUSION: The optimal duration can be estimated by the t 97 , which can be achieved in less than 3 minutes and differs across ablation targets. TDE expansion decelerates with prolonged ablation. Future studies are needed to examine the radiographic and clinical outcomes as well as the effects of ablation power, irrigation speed, and the effect of previous therapies on ablation dynamics.
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