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Computer Assisted Planning for Curved Laser Interstitial Thermal Therapy

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Laser interstitial thermal therapy (LiTT) is a minimally invasive alternative to conventional open surgery for drug-resistant focal mesial temporal lobe epilepsy (MTLE). Recent studies suggest that higher seizure freedom rates are correlated with maximal ablation of the amygdala-hippocampal complex (AHC), whilst sparing of the parahippocampal gyrus (PHG) may reduce neuropsychological sequelae.

Current commercially available laser catheters are inserted following manually planned straight-line trajectories, which cannot conform to curved brain structures, such as the hippocampus, without causing collateral damage or requiring multiple insertions. The clinical feasibility and potential of curved LiTT trajectories through steerable needles has yet to be investigated. This is the focus of our work.

We propose a GPU-accelerated computer-assisted planning (CAP) algorithm for steerable needle insertions that generates optimized curved 3D trajectories with maximal ablation of the AHC and minimal collateral damage to nearby structures, while accounting for a variable ablation diameter.

The algorithm is validated through a detailed retrospective study on clinical epilepsy patient data, showing the potential advantage of following a curved path in the brain for both insertion and ablation purposes. Curved trajectories that follow the contours of given anatomy, as the AHC in the case of refractory epilepsy, were associated with a statistically significant improvement compared to their straight counterpart. Benefits were measured in terms of several quantitative metrics including percentage coverage of the ablation region and a published risk score to quantify, among other aspects, the safe distance between the ablation trajectory and critical brain regions.

This is the first clinical application of preoperative planning for steerable needle-based LiTT. This study suggests that steerable needles have the potential to improve LiTT procedure efficacy whilst improving safety and should thus be investigated further.

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