Assessment of irrigation dynamics in magnetic-resonance guided laser induced thermal therapy (MRgLITT)

Magnetic-Resonance Guided Laser-Induced Thermal Therapy (MRgLITT) is a minimally-invasive ablation procedure for treating intracranial pathology using laser energy delivered through a fiber-optic. Saline irrigation is used to cool the fiber-optic, but factors affecting irrigation efficacy are not well studied, and quantitative information regarding irrigation speed and volume during MRgLITT procedures have not been reported. Here, we aimed to characterize variables affecting irrigation efficacy in MRgLITT.

We investigated the irrigation setup of the Visualase thermal therapy system during MRgLITT procedures (Visualase Inc., Houston, TX). Using the system's peristaltic pump, irrigation flow rate was quantitated by measuring volume over five one-minute intervals. Pump settings 1-10 were assessed with and without the position-locking, resistance-imparting bone anchor in both single and double-catheter setups. Multiple tightness settings of the bone anchor were tested, and flow rates were analyzed.

Rate of flow increased non-linearly with pump setting (F(1,4) = 2168.86; P < 0.001) in both single and double catheter setups. The lowest pump setting had a flow rate of 24 cc/min, while the highest setting was 36 cc/min. The rate of change in flow successively decreased without plateau. Tightness setting of the bone anchor affected flow in a reverse sigmoid pattern, with no impact on rate until after two quarter-turns, which produced a marked decrease in flow up to one-half of the initial rate (F(1,4) = 12818.96; P < 0.001).

Flow rate through the cooling catheter in MRgLITT follows a non-linear pattern with increasing peristaltic pump speed. This rate is subject to significant changes when the bone anchor is tightened more than two quarter-turns. These findings serve as a foundation for future studies aimed at understanding the effect of irrigation speeds in achieving optimal ablation volumes.