Grant: Travel Awards - Institute Community Support

The goal of this project is to develop a novel method for improving the accuracy of tissue oxygenation measurements. Tissue oxygenation, most commonly reported as the oxygen saturation (sO2) is a crucial metric in conditions such as cardiovascular disease, diabetes and cancer. Many techniques have been developed for estimating in-vivo tissue sO2. However they are either invasive (requiring the use of needles), utilize radioactive tracers (increasing the dose to healthy tissue) or are too expensive for routine monitoring (ex. using magnetic resonance imaging). There is a need for a cheap, non-invasive and high resolution method applicable to a wide range of clinical scenarios. Photoacoustic (PA) imaging has emerged as a modality which provides simultaneous tissue structural and functional information. It can measure absolute tissue sO2 for depths up to a few-hundred microns since light distribution (required for PA signal generation) is uniform at shallow depths. However, in clinically relevant anatomical sites (ex. breast, kidney, liver, muscle etc.), light penetration is subject to significant attenuation, rendering sO2 estimates erroneous beyond a few millimeters. We have developed a technique to compensate depth-dependent errors thus improving the accuracy of PA imaging in probing deep tissue oxygenation. In this study, mice will be used to demonstrate the in-vivo validity of our developed technique. The oxygenation of the muscle will be probed using a commercial PA imaging device. The mice will be exposed to various levels of oxygen to change the tissue sO2. Live animals must be used for this experiment as active cardiovascular and pulmonary systems are required to observe the impact that breathing gases have on the oxygenation of target organs. The results demonstrate significant improvement in the measured oxygenation with depth.