Non-invasive techniques for quantifying blood flow, vascular remodeling and blood oxygen saturation (SaO2) down to capillary-level resolution are of paramount importance for the improved understanding, diagnosis and treatment of neurovascular and neurometabolic disorders such as stroke. Currently there are no imaging techniques that can non-invasively and simultaneously measure these parameters without the use of exogenous contrast agents in the microcirculation in vivo. We have pioneered a non-invasive 3D optical imaging technology, optical microangiography (OMAG), that meets this challenge. In the parent R01 project, we have successfully demonstrated that OMAG generates real-time 3D images of both tissue structure and blood flow at capillary level resolution with an imaging depth up to 2 mm without the need for exogenous contrast agents (see publication list in the progress report). In addition, we also demonstrated a number of novel methods to successfully extract the blood flow signals from huge 'noise' background of optical scattering, an obstacle married with almost all high-resolution optical imaging techniques. As a direct result of our research, it is now practical to image functional 3D microvascular networks in pre-clinical (small animal models) and clinical settings (human retina). Since our first publication that reported OMAG, the field has grown exponentially, and there are several companies planning to market the OMAG product. Now that we have successfully developed OMAG for imaging functional microcirculations, we will direct our research efforts towards the development of the next generation OMAG imaging modality. This next generation technology will allow depth-resolved cerebral blood flow (CBF), microvascular morphology and SaO2 at the capillary level to be simultaneously monitored within a scanned tissue volume. To achieve this goal, we will first develop a multifunctional OMAG (mfOMAG) system capable of measuring rapid and long term responses of cerebral blood flow and oxygenation. We will then combine this system with a novel spectral laser-speckle imaging which we will use as a guide to immediately hone into injured regions for a thorough evaluation with mfOMAG. Finally, we will determine the utility of mfOMAG for serial monitoring of cerebral blood flow changes and vascular remodeling following experimental stroke in mice.
We propose to develop a novel, non-invasive optical imaging technology that can simultaneously provide quantitative assessment of cerebral blood flow and blood oxygenation in the brain of small animal models with the skull left intact. This novel imaging technique will become an important tool to investigate the cerebral vascular responses to an ischemic injury, and may help diagnosis, monitoring, and therapeutic interventions for other diseases with vascular involvement.
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