A Cost-Benefits Analysis of Different Transducer Components for Simultaneous Trans-Spinal Magnetic and Low-Intensity Focal Ultrasound Stimulation.

Chronic neuropathic back and leg pain are among the leading indications for spinal cord stimulation (SCS) in the U.S. Although this approach has proven effective, it is highly invasive and sometimes associated with surgical risks and possible complications. A novel multimodal device was developed to expand the therapeutic options and provide a safer treatment alternative, combining the deep and focal targeting of low-intensity focused ultrasound (LiFU) with the safety and bone penetration advantages of trans-spinal magnetic stimulation (TSMS). The device includes a LiFU transducer (with a piezoelectric crystal and a tungsten piston) embedded in a low-impedance figure-of-eight TSMS coil and a thermal sensor for safety monitoring.Finite element method (FEM) simulations estimated key parameters, such as electric fields in the spinal cord, validated through direct dB/dt measurements. The electromagnetic impedance measurements of the transducer were performed in three cases: unloaded (no transducer), preloaded (no tungsten piston), and postloaded. We studied the performance of magnetic stimulation versus the various transducer loading conditions to understand the costs and benefits of each setup. The results show that the peak Electric Field magnitude in the rat's spinal cord was 225 V/m postloaded, 324 V/m preloaded, and 429 V/m unloaded. This study provides critical insights into the design trade-offs for optimizing simultaneous TSMS and LIFU neuromodulation.Clinical Relevance-This technology offers safer, non-invasive, and non-pharmacological solutions, addressing unmet needs in chronic pain management and potentially transforming care for neuropathic pain patients. The outcome will allow for the first non-invasive multimodal thoracic spinal cord stimulation to treat sciatica.