Neuronavigation-Guided Transcranial Acoustoelectric Brain Imaging: A New Modality for High Resolution Electrical Brain Mapping.

Abstract

Although functional magnetic resonance imaging (fMRI) and scalp electroencephalography (EEG) are powerful tools to study the human brain and behavior for many clinical and research applications, they are limited in both resolution and accuracy. Transcranial Acoustoelectric Brain Imaging (tABI) is a new modality that combines focused ultrasound with electrical sensing to map electrical currents at the millimeter and millisecond scales. The aims of this study are to demonstrate the feasibility and assess performance of integrating tABI with a neuronavigation system to map deep dipoles in a head model with a human skull. Feedback from the neuronavigation system with optical tracking and imported MRIs helped place a 2D 0.6 MHz ultrasound array on the skull to target selected regions inside the head. An electrode array placed inside the conductive "brain" gel generated sources for imaging. 4D tABI scans produced volumetric time-varying electrical maps co-registered with anatomical MRI. Spatial resolution was better than 5 mm for current sources at depth >20 mm and a current detection threshold better than 500 μA at 1 MPa with an image registration error of <6.5 mm. Neuronavigation-guided tABI provides accurate and high resolution detection of deep current sources in a human head model. This study is a key steppingstone towards pushing the limits of tABI and developing a novel, disruptive modality for noninvasive electrical brain imaging in humans.