Sensitivity distribution simulations of surface electrode configurations for electrical impedance myography.

INTRODUCTION: Surface-based electrical impedance myography (EIM) is sensitive to muscle condition in neuromuscular disorders. However, the specific contribution of muscle to the obtained EIM values is unknown.

METHODS: We combined theory and the finite element method to calculate the electrical current distribution in a 3-dimensional model using different electrode array designs and subcutaneous fat thicknesses (SFTs). Through a sensitivity analysis, we decoupled the contribution of muscle from other surrounding tissues in the measured surface impedance values.

RESULTS: The contribution of muscle to surface EIM values varied greatly depending on the electrode array size and the SFT. For example, the contribution of muscle with 6-mm SFT was 8% for a small array compared with 32% for a large array.

CONCLUSIONS: The approach presented can be employed to inform the design of robust EIM electrode configurations that maximize the contribution of muscle across the disease and injury spectrum. Muscle Nerve 56: 887-895, 2017.