Concurrent enhancement of imaging depth and contrast for optical coherencetomography by hyperosmotic agents

The highly scattering nature of nontransparent human tissue limits the imag ing depth of optical coherence tomography (OCT) to 1-2 mm. When the longer wavelength of the light source is used; the penetration depth is improved; however, the imaging contrast is decreased, largely because of reduced back scattering at the microscopic scale and reduced refractive heterogeneity of the macroscopic scale. For a more effective diagnosis using OCT, a concurr ent improvement of penetration depth and imaging contrast is often needed. We report that the OCT imaging depth and contrast can be enhanced concurren tly by the use of osmotic agents. Imaging depth enhancement by application of a chemical agent is not new; however, to our knowledge; imaging contrast enhancement has not been reported in the literature. Our hypothesis is tha t the latter is due to localized dehydration. We demonstrate experimentally , by examples, that topical applications of glycerol and propylene glycol, two common biocompatible and osmotically active solutions, onto the surface of rat tissue could significantly improve its OCT imaging contrast and dep th capability. (C) 2001 Optical Society of America.