Head phantoms for bioelectromagnetic applications: a material study.

Area of Science:

• Biomedical Engineering
• Materials Science

Background:

• Accurate physical head phantoms are crucial for validating electroencephalography (EEG) and transcranial electrical stimulation (TES) models.
• Synthetic materials with stable mechanical and electrochemical properties are needed to mimic human head tissue conductivity.

Purpose of the Study:

• To characterize the electrical conductivity of synthetic materials for creating realistic head phantoms.
• To evaluate agarose, gypsum, and NaCl solutions as surrogates for scalp, skull, and intracranial volumes.
• To assess the suitability of reed sticks for modeling anisotropic white matter conductivity.

Main Methods:

• Measured impedance of agarose hydrogel, gypsum, and NaCl solutions using a four-electrode setup.
• Calculated electrical conductivity from impedance measurements.
• Measured anisotropic conductivity of reed sticks immersed in NaCl solution.

Main Results:

• Achieved conductivities for agarose (0.30-0.31 S/m), gypsum (0.0017-0.0425 S/m), and NaCl solution (0.332 S/m) within established ranges.
• Reed sticks exhibited anisotropic conductivity with a 1:2.8 ratio.
• All tested materials demonstrated conductivity values suitable for EEG and TES modeling.

Conclusions:

• Agarose, gypsum, and NaCl solutions are suitable, stable materials for representing the scalp, skull, and intracranial compartments of the head.
• Tailored reed sticks can effectively model anisotropic conductivity found in white matter fiber tracts.