Visible-light OCT spectrometer for microvascular oximetry

摘要

We describe a visible-light spectroscopic OCT system designed to obtain localized measurements of hemoglobin oxygenation in the superficial microcirculation and also to obtain localized measurements of optical properties at visible wavelengths. The device is based on a supercontinuum source emitting in the 450-600 nm spectral range, which overlaps the visible absorption band of hemoglobin. The OCT detection system uses a spectral domain set-up using a linear CCD and home-built spectrometer and is implemented in single-mode fiber. Multi-spectral OCT images can be acquired at eight wavelengths simultaneously each with 256 axial pixels, and multi-linear regression processing can be applied at a line-rate of 1 kHz. The dynamic range of the system is characterized and found to be limited by excess noise in the supercontinuum source. The wavelength-dependence of scatter is determined for Intralipid using a single-scatter model. Coherent back-scatter from whole blood is detected in the visible spectrum and used to infer the total attenuation coefficient at 470 nm. The feasibility of obtaining oximetry data over volumes of blood as thin as 20 microns is demonstrated. The work describes first steps towards assessment of hemoglobin oxygenation in the superficial microcirculation with picoliter resolution.