BME Seminar Series: Dr. Vivek Srinivasan

Coherent Optical Techniques for Structural and Functional Neuroimaging

Instructor, Photon Migration Imaging Laboratory, Massachusetts General Hospital, Massachusetts Institute of Technology, Harvard Medical School

Abstract

Optical imaging methods have significantly impacted the field of neuroimaging and are now widely used in studies of cellular and vascular physiology and pathology in the living brain. However, optical imaging modalities are characterized by a trade-off between penetration depth and resolution. Diffuse optical imaging methods achieve millimeter spatial resolutions and centimetre penetration depths. On the other extreme, two-photon microscopy achieves sub-micron spatial resolution and penetration depths of up to half a millimetre. Coherent optical imaging techniques (such as Optical Coherence Tomography) have the potential to bridge the gap between these two regimes, enabling investigation of cortical depths previously inaccessible with microscopy. Instead of fluorescent labelling, image processing is used to enhance contrast arising from endogenous tissue scattering. We have developed coherent optical methods for quantification of absolute cortical blood flow, capillary perfusion, myelination, neuronal density, and the distribution of capillary velocities in vivo with laminar resolution, at cortical depths exceeding 1 mm. We present applications of these techniques to investigate laminar neurovascular coupling and longitudinal remodelling in experimental models of ischemic stroke.