Use of near-infrared fluorescent dyes in depth resolved spectroscopic optical coherence tomography.

Optical coherence tomography (OCT) images of biological tissues often have low contrast. Spectroscopic OCT (SOCT) methods have been developed to enhance contrast. Due to the time-frequency "uncertainty principle" in SOCT signal analysis, minute spectral changes can not be detected for high spatial resolution applications. In order to enhance SOCT contrast in tissues with low inherent spectral absorption, we developed a contrast enhancing technique using near-infrared (NIR) dyes. We developed an optimized algorithm for SOCT and an optimum dye concentration for imaging. The effect of contrast enhancement was studied both in tissue phantoms and in situ experiments. Contrast-enhanced images are compared with fluorescence microscopy, demonstrating a link between SOCT and fluorescence imaging.