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

TLDR

OCT penetration is limited to 1–2 mm in scattering tissues, and while longer wavelengths increase depth, they reduce contrast due to diminished backscattering and refractive heterogeneity, necessitating a method that improves both depth and contrast simultaneously. The study tests whether osmotic agents can concurrently increase OCT imaging depth and contrast, hypothesizing that localized dehydration underlies the contrast improvement. Topical application of biocompatible osmotically active solutions glycerol and propylene glycol to rat tissue surfaces was used to assess their effect on OCT imaging. The experiments showed that these agents significantly enhanced both OCT imaging depth and contrast, achieving concurrent improvement.

Abstract

The highly scattering nature of nontransparent human tissue limits the imaging 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 backscattering at the microscopic scale and reduced refractive heterogeneity of the macroscopic scale. For a more effective diagnosis using OCT, a concurrent improvement of penetration depth and imaging contrast is often needed. We report that the OCT imaging depth and contrast can be enhanced concurrently 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 that 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 depth capability.