Noninvasive laser-induced photoacoustic tomography for functional imaging

Abstract

While brain imaging and electrophysiology play a central role in neuroscience research and in the evaluation of neurological disorders, a single noninvasive modality that offers both high spatial and temporal resolution is currently not available. In this chapter, we describe an emerging optical imaging technique called photoacoustic tomography (PAT) which can noninvasively track brain hemodynamics with both high spatial and temporal resolution, and at a depth that is clinically relevant. We present in detail photoacoustic reconstruction methods and imaging systems. Using a rodent model of acute focal epilepsy, we demonstrate the noninvasive yet whole surface and depth capabilities of the PAT system that allow to actually see what is happening during ictogenesis in terms of seizure onset and spread. Both seizure onset and propagation are tomographically detected at a spatial resolution of 150 μm and a temporal resolution of 300 ms. Dynamical changes of vasculature during epileptiform events are also detected with high spatiotemporal resolution. Together, these findings suggest that PAT represents a powerful tool for noninvasively mapping seizure onset and propagation patterns, and the “functional” connectivity within epileptic brain networks.