Improved phase-resolved optical Doppler tomography using the Kasai velocity estimator and histogram segmentation

Significant improvements are reported in the measurable velocity range and tissue motion artefact rejection of a phase-resolved optical coherence tomography and optical Doppler tomography system. Phase information derived from an in-phase and quadrature demodulator is used to estimate the mean blood flow velocity by the Kasai autocorrelation algorithm. A histogram-based velocity segmentation algorithm is used to determine block tissue movement and remove tissue motion artefacts that can be faster or slower in velocity than that of the microcirculation. The minimum detectable Doppler frequency is about 100 Hz, corresponding to a flow velocity resolution of 30 mum/s with an axial-line scanning frequency of 8.05 kHz and a mean phase change measured over eight sequential scans: the maximum detectable Doppler frequency is +/-4 kHz (for bi-directional flow) before phase wrap-around. (C) 2002 Elsevier Science B.V. All rights reserved.