A multimodal brain phantom for noninvasive neuromodulation

Abstract

Noninvasive neuromodulation enables brain stimulation without surgery but requires precise optimization of stimulation parameters to ensure efficacy and safety. Direct testing on human or animal subjects is costly, time intensive, and constrained by ethical and safety considerations. To address these challenges, a low-cost, versatile brain phantom was designed to emulate key biophysical properties across multiple neuromodulation modalities. The phantom was fabricated using ground beef, sodium alginate, and starch, and cast within a custom 3D printed mold. A multimodal test platform was created and validated by integrating established principles from low-intensity focused ultrasound (LIFU), transcranial direct current stimulation (tDCS), and thermal phantom design. Numerical simulations predicted a LIFU peak negative pressure of 0.631 MPa, closely matching the target Pr.3 value, with negligible temperature elevation (<0.01 {degrees}C). Consistent with prior reports, tDCS exposure did not induce lasting alterations in the phantoms physical or electrical properties. The electrical conductivity was 0.11{+/-}0.02 S/m, reflecting water saturation within the phantom matrix; the thermal conductivity averaged 0.557 W/(mK), consistent with reported values for brain tissue analogs. This study primarily evaluated LIFU and tDCS performance; future work should extend characterization to additional modalities such as deep brain stimulation and transcranial magnetic stimulation. Further assessment of the phantoms optical properties would also facilitate photobiomodulation and photoacoustic imaging studies. Overall, this inexpensive, easily fabricated phantom presents a practical and adaptable platform for multimodal neuromodulation research and parameter optimization.