Treating Epilepsy via Thermal Ablation: Initial Experiments With an MRI-Guided Concentric Tube Robot

Abstract

Epilepsy is a prevalent neurological disorder affecting 65 million people globally [1]. Anti-epileptic medications fail to provide effective seizure control for 30% of patients, placing them at a 7–17% risk of Sudden Unexplained Death in Epilepsy and recurrent seizures. Surgical resection of the seizure focus is a potentially curative treatment for patients with seizures that electrophysiologically correlate to a focal lesion. For these patients, focal surgical resection can result in 60–70% seizure-freedom rates [2]. However, open resection carries the risk of cognitive impairment or focal neurologic deficit [3]. Recent innovations in MRI enable high resolution soft tissue visualization, and real-time temperature monitoring, making MR-guided ablation therapy a promising minimally invasive technique to restrict the tissue destruction to just the seizure focus. Commercial products (e.g., Visualase, Medtronic Inc.; ClearPoint, MRI Interventions Inc.; NeuroBlate, Monteris Inc.) have recently been introduced for MR-guided laser-based thermal ablation. These products require the physician drill a hole into the skull for ablation probe placement, and may not always be able to ablate the entire seizure focus when the structure has a curved shape (such as the hippocampus) [4]. Incomplete ablation of the seizure focus would lead to seizure recurrence. We have recently proposed concentric-tube steerable needles as a means to address these challenges [4–7]. They enable nonlinear trajectories and offer the potential to enter the brain through the patient’s cheek via a natural opening in the skull base (i.e. the foramen ovale). We have designed and fabricated an MR-compatible robotic system to provide high resolution actuation for helical needle deployment [5]. We have shown in simulation that the curved medial axis of hippocampus can be accessed via a helical needle that delivers the ablation probe into the brain [4]. These preliminary results suggest that MR-guided robotic transforamenal thermal therapy could potentially provide a less invasive approach for potentially curative epilepsy treatment. In this paper we present our first results delivering heat along curved paths in brain phantoms and imaging the resulting treatment zones using MRI.

Computer Assisted Planning for Curved Laser Interstitial Thermal Therapy

“…A curved trajectory through a steerable needle could provide a better trade-off between coverage of the target area and damage reduction to collateral structures, while facilitating the inclusion of EnCx and PiCx, as recently reported in terms of Engel I outcomes for correlated structures [16], [23]. D.Comber et al [24] proposed a patient-specific design of concentric tube needles for a transforamenal approach to access the hippocampus. In this study, for each of the 20 selected hippocampi, a concentric tube robot was designed and optimized to traverse a trajectory from the foramen ovale to and through the hippocampus, from head to tail.…”

Curvature-based force estimation for an elastic tube

“…For example, Bajo et al [8,9] proposed a method for tendon-driven continuum robot contact force sensing, but this requires a dedicated force cell at the actuation unit. The joint-space force cells may not be available for some continuum devices such as concentric tubes [10], steerable needles [11], or in MR-guided interventions [12][13][14][15] where the MRI-conditional force sensor is not readily available. 1 Alternatively, force can be estimated implicitly based on the measurements of continuum robot configuration change.…”