Complex fast phase unwrapping method for Doppler OCT

We present a modified Fast Phase Unwrapping (FPU) algorithm and its application for calculation of the axial flow velocity and volumetric flow rate in Doppler optical coherence tomography (DOCT). We outline the FPU method and show that it can be implemented in Fourier-domain optical coherence tomography using Fourier transformations (4FT). We present two-dimensional (2D) and three-dimensional (3D) realizations of the algorithm to reconstruct unwrapped phase in numerical simulations, as well as in data collected from phantom. We demonstrate that the phase unwrapping outcomes of the 2D and 3D 4FT FPU algorithms depend on the phase noise in the input data. For low phase noise data both algorithms generate reliable results. With increasing noise, the 2D algorithm starts generating phase unwrapping errors earlier than the 3D version. With the phase noise larger than a limiting value, none of the algorithms provides error-free results. We demonstrate that within their phase noise applicability limits, the phase unwrapping methods enable calculation of volumetric flow rates in the flow phantom even in the presence of phase wraps. We demonstrate that application of phase unwrapping methods enables extension of the measurable flow velocities beyond the phase range limitation of the Doppler OCT data.