A Planning Environment for Intracranial Electric Field Treatment of Brain Tumors
E Iredale1*, B Voigt1, A Rankin2, K Kim1, J Chen1, S Schmid1, M Hebb1, T Peters1,2, E Wong1, (1) Western University, London, ON, CA, (2) Robarts Research Institute, London, ON, CA
Presentations
MO-F-BRC-2 (Monday, 7/11/2022) 1:45 PM - 2:45 PM [Eastern Time (GMT-4)]
Ballroom C
Purpose: To develop an Intratumoral Modulation Therapy (IMT) planning system for the treatment of malignant brain tumors using modulated low-intensity electric fields delivered via multiple implanted electrodes.
Methods: The IMT planning system was created via a custom coded application in 3D Slicer, designed to incorporate patient image segmentation and smoothing, electrode trajectory planning, optimization of electrode tip coordinates, stimulation voltage and phase shift, to maximally cover the tumor with the prescription electric field, and the visualization of the results. A brain phantom was used to implement the full planning and optimization pipeline, robotically implant electrodes at planned trajectories, and measure the voltage and phase shift to validate electric field delivery. Post-operative stimulation parameter re-optimization was included in the system to accommodate electrode placement uncertainty.
Results: The IMT treatment planning system uses a semi-automated pipeline, where based on the patient image in 3D Slicer, a user can select electrode entry points and initial trajectories. Keeping the electrode entry points fixed, the TPS can simultaneously optimize non-parallel electrode trajectories and stimulation parameters. Robotic implantation of four stimulating electrodes and two measurement electrodes resulted in 1.1 ± 0.6 mm tip separation offset and 1.2 ± 0.6° offset in the angle between electrode pairs. Geometrical uncertainty impacted electric field coverage by a maximum 2.6%, and phase shift uncertainty from voltage measurements impacted coverage by less than 0.4%. The impact of non-optimal electric field coverage was mitigated through voltage and phase shift re-optimization post-implantation.
Conclusion: The transition from simplified spherical tumor models with parallel electrodes to the semi-automatic patient specific treatment planning system incorporating non-parallel electrode trajectories has enabled the expansion to future clinical investigations. Validation of the IMT planning pipeline with robot-assisted electrode implantation, post-operative stimulation parameter re-optimization and delivered voltage lays the groundwork for upcoming patient clinical trials.
Funding Support, Disclosures, and Conflict of Interest: Funding: NSERC CGS-D, NSERC Idea to Innovation Grant, NSERC Discovery Grant, Cancer Research Society, the Canada Foundation for Innovation, and the Western Innovation Fund. COI: Patent (granted) CA2985847 entitled Intratumoral Modulation Therapy. Provisional Patent (filed) WO2021142549 entitled Planning and delivery of dynamically oriented electric field for biomedical applications.
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