Development of a phase-resolved Doppler optical coherence tomography system for use in cutaneous microcirculation research

Abstract

Phase-resolved Doppler optical coherence tomography is a recently reported technique for simultaneously imaging tissue structure and blood with high velocity resolution. The optical set-up consists of a fibre-based Michelson interferometer with a 1300nm superluminescent diode in the source arm. The output power is 0.6mW with a bandwidth of 50nm. The reference arm contains a grating-based Fourier domain rapid-scanning delay line with an electro-optic phase modulator to provide a stable reference frequency (800kHz). Ten axial scans sampled, at 400Hz, from the same location are processed to generate structural and velocity data from the reconstructed phase information derived from a Hilbert transform. The sample arm probe focuses light from the fibre into the tissue, producing a beam spot of diameter approximately 20micrometers . The probe is mounted on a linear translation stage, which generates a lateral step of 10micrometers between groups of ten axial scans. The Doppler shift in each pixel is calculated from the average phase shift over the ten sequential scans at each location. The acquisition time for a 100x100 pixel image is approximately 5s. We demonstrate the systems ability to image in-vivo changes in skin perfusion, induced by standard non-invasive physiological techniques.