4D Acoustoelectric Imaging of Current Sources in a Human Head Phantom

Electrical brain mapping typically suffers from poor spatial resolution due to the uncertain spread of electric field lines through the brain and skull. To overcome this limitation, we propose 4D acoustoelectric brain imaging (ABI) for mapping current densities at a spatial resolution confined to the ultrasound (US) focal spot. Acoustoelectric (AE) imaging exploits an interaction between a pressure wave and tissue resistivity. It has been used to dynamically map the cardiac activation wave in the live rabbit heart. Our long-term goal is to extend this technique for electrical mapping of the human brain. In this study, we developed a human-size head and brain phantom to test and optimize ABI for detecting an embedded "EEG-Iike" electrical current. Detection thresholds for current sources more than 15 mm below the surface of the brain phantom was less than 1 mA/cm(2) using a 0.5-MHz or 1 MHz single element transducer and copper recording wires. Further optimization of ABI could enable detection of small neural currents in the brain and lead to a new modality for functional brain imaging.