Optimized Transcutaneous Spinal Cord Direct Current Stimulation using Multiple Electrodes from 3/9/7 System

Transcutaneous spinal cord direct current stimulation (tSDCS) has been applied as an easy non-invasive approach to modulate spinal cord functions. Currently there is no formal layout or guidelines for electrode placement to optimize tSDCS. Most clinical applications simply place the stimulating electrode over the intended spinal cord target. Here we show that this ad hoc method cannot achieve optimal stimulation. Specifically, we propose a new electrode layout for optimized tSDCS. The candidate high-definition electrodes distribute on the back of the body evenly and the layout was named 3/9/7 system. Algorithmic optimization was performed leveraging this electrode placement system and a 1 mm3 human full body model. Results show that the optimal stimulation montages cannot be trivially determined and they outperform the unoptimized stimulation configuration. This work opens the possibility for systematic treatment planning in future clinical applications of tSDCS.