Patient-Specific Electric Field Simulation In Spinal Metastasis Electrochemotherapy.

Electrochemotherapy (ECT) combines the administration of cytotoxic agents with high-voltage electric pulses that transiently permeabilize tumor cell membranes and enhance intracellular drug uptake. This minimally invasive, nonthermal technique is particularly suitable for tumors located near critical structures, where surgery, radiotherapy, or percutaneous thermal ablation may be limited. In the spine, ECT can provide pain relief, neural decompression, and local tumor control while preserving neural structures. However, its implementation remains challenging due to complex vertebral anatomy, limited understanding of electric field distribution, the absence of dedicated planning tools, and the risk of neural injury. This protocol describes a reproducible workflow for patient-specific electric field simulation in spinal ECT. Multimodal imaging combining CT and MRI enables reconstruction of tumoral, vertebral, neural, and soft-tissue anatomy using semi-automatic and manual segmentations performed within the open-source 3D Slicer platform. Tissue conductivities are assigned according to the IT'IS database, and linear finite-element simulations (constant conductivity) are performed with AI4DEEP, a dedicated 3D Slicer module, to compute 3D electric field maps across multiple isodose thresholds. Follow-up contrast-enhanced MRI is used for validation through Dice similarity coefficients comparing simulated isoelectric field volumes with post-ECT necrotic tumoral areas. Qualitative comparison of simulated electric field maps, follow-up MRI, and clinical outcomes was performed by expert interventional radiologists to evaluate the ability of the software to predict undertreated and overtreated regions. Nine ECT procedures were processed to assess the workflow. The highest concordance between simulated electric field and post-ECT necrosis was observed in the 160-200 V/cm range in this specific clinical and numerical setting. The workflow also identified regions of insufficient or excessive treatment, consistent with clinical and imaging follow-up. The described workflow lays the groundwork for reproducible ECT planning, supporting optimized electrode placement and parameter adjustment to improve safety and efficacy in complex spinal ECT procedures.