A Lumped RC Equivalent Circuit Model of Head Tissues in sub-MHz Frequency Regimes
This work provides a computationally efficient alternative to numerical methods for rapid prototyping and real-time simulations in neuro-sensing and neuro-stimulation system design.
The authors developed a lumped RC equivalent circuit model for head tissues operating up to 50 kHz, achieving close agreement with semi-analytical solutions for scalp voltage peaks across varying skull thicknesses and dipole eccentricities.
Accurate modeling of electric potential and current distribution in head tissues is crucial for the design and evaluation of neuro-sensing and neuro-stimulation systems operating in the sub megahertz frequency range. Numerical methods are widely employed in electromagnetic simulations, however their computational cost can limit their applicability to rapid prototyping, real-time simulations, and circuit-level integration. In this work, we introduce a lumped RC equivalent circuit model that reproduces the electrical behavior of a canonical three-layer spherical head geometry over a frequency range up to 50 kHz. The model accounts for frequency-dependent tissue conductivity and permittivity to capture dispersive effects, employing complex conductivity in the electro-quasi-static (EQS) regime. The circuit topology uses a minimal set of impedance elements in order to represent the essential mechanisms of electric signal propagation. Validation was performed using a dipolar brain source configuration for scalp voltage peak estimation, showing close agreement with semi-analytical solutions across different skull thicknesses and dipole eccentricities. In addition, the impact of tissue dispersion and displacement current inclusion on the model accuracy was quantitatively assessed, highlighting their contribution to the overall fidelity of the proposed approach.