Effects of variable power on tissue ablation dynamics during magnetic resonance-guided laser-induced thermal therapy with the Visualase system

Purpose: Magnetic resonance-guided laser-induced thermal therapy (MRgLITT) is a minimally invasive procedure used to treat various intracranial pathologies. This study investigated the effects of variable power on maximal estimated thermal damage during ablation and duration required to reach maximal ablation. Materials/Methods: All ablations were performed using the Visualase Thermal Therapy System (Medtronic Inc., Minneapolis, Minnesota), which uses a 980 nm diffusing tip diode laser. Cases were stratified into low, medium and high power. Maximal thermal damage estimate (TDE _max ) achieved in a single plane and time to reach maximal damage (t _tdemax ) were measured and compared between groups using a 2×3 Fixed Factor Analysis of Covariance. Ablation area change for cases in which an initial thermal dose was followed by a subsequent dose, with increased power, was also assessed. Results: We used real-time ablation data from 93 patients across various intracranial pathologies. t _tdemax (mean ± SEM) decreased linearly as power increased (low: 139.2 ± 10.4 s, medium: 127.5 ± 4.3 s, high: 103.7 ± 5.8 s). In cases where a second thermal dose was delivered at higher power, the TDE expanded an average of 51.4 mm ² beyond the initial TDE generated by the first ablation, with the second ablation approaching TDE _max at a higher rate than the initial ablation. Conclusion: Increased power results in a larger TDE _max and an increased ablation rate. In cases where an initial thermal dose does not fully ablate the target lesion, a second ablation at higher power can increase the area of ablation with an increased ablation rate.