Enhancement of Light Propagation in Tissue Using Hyper-Osmotic Agents

University Of Texas At Austin, Austin TX

Investigators

Abstract

9986296 Welch We have shown that hyperosmotic solutions of dextrose, glycerol, hypaque, and polyethylene glycol reduce light scattering in tissue; local regions containing the hyperosmotic agent become transparent. The mechanisms for reducing scattering are believed to be index of refraction matching of the hyper-osmotic agent with tissue constituents such as collagen and tissue dehydration. This macro- and microscopic index matching decreases internal light scattering, which increases transmittance and decreases reflectance (back scattering) of a sample of skin. The use of chemical agents will provide a technique for locating sources of scattering and evaluating the contribution of tissue constituents to scattering. This will increase our knowledge of light propagation in tissue at the micro and macro levels. The dynamics of the process are dependent upon the mass transfer of the hyper-osmotic agents and water. Optical measurements such as local transmittance using optical fibers and Optical Coherence Tomography (OCT) will be combined with computations obtained from a network thermodynamic model to evaluate mass transport throughout skin as a function of time. The proposed research will elucidate the mechanisms of tissue clearing and determine the feasibility of using hyper-osmotic agents to enhance light-based diagnostic and treatment procedures. We anticipate that the working depth of fluorescence spectroscopy and confocal imaging can be increased by a factor of five to ten. In addition, it should be possible to image blood vessels in skin using CDOCT. Demonstration of these enhancements will establish the feasibility of potential diagnostic applications for this basic science. These applications include skin morphologic examination, skin, bladder, GI and mucosal tumor identification, and non-invasive blood glucose measurement. Potential therapeutic applications include hair removal, ablation of deep stromal tumors, leg vein coagulation, photodynamic therapy (PDT) of tumors, targeting of individual dermal vessels, transscleral photocoagulation, and endoscopic surgery of the bladder, prostate, and GI tract.