Transcranial Acoustoelectric Imaging of Spatially and Temporally Varying Electrical Currents to Better Understand Neuronal Dysfunction

To effectively diagnosis epilepsy, Scalp Electroencephalography (EEG) alone fails to offer what Transcranial Acoustoelectric Brain Imaging (tABI) can. Invasive Depth Electrode (DE) EEG techniques may achieve localized detection of neuronal function and noninvasive scalp EEG sacrifice accuracy of signal detection for safety. To achieve our goal of noninvasively visualizing travelling current densities of the brain at varying locations and times, determine signal detection limits and calculate conduction velocities of travelling deep neuronal waves. We proposed a method to detect signal profiles that changed over a period of 50 ms and 35mm distance. Neural currents were simulated ex-vivo in a human head model using a 12-site Spencer/AdTech Depth Electrode (DE). Slow ≤ 200 Hz and varying magnitude signals were used to emulate neuronal signals in an agarose/saline gel brain phantom inside a human skull. Transcranial Acoustoelectric Brain Images (tABI) and movies were produced using a 0.6 MHz center frequency 2D Ultrasound (US) array. These movies provide demonstrable evidence that we can effectively correct for transcranial US imaging of specific current locations with millimeter (mm) and millisecond (ms) accuracy. More specifically, we can track these signals as they travel spatially and temporally regardless of their direction of travel. Conduction velocities were found through tracking centroid peak magnitude coordinates (x,y,z) over time to map more effectively specific (1.5mm and 4.5mm site separation on Infinity and AdTech electrodes, respectively) spanning wide field of view (35mm) at sub-cranial depth of ~30mm. Detection limits were nominally found to be ≤ 300µA. This tABI technique offers safe, accurate and less expensive route to better diagnosing epileptic (ictal) signals in the human brain model.