Vector Doppler Optical Coherence Tomography

The interest in developing a vector Doppler technique lies in the capability of this investigation technique to extract quantitative ("true" velocity vector) and accurate information about blood flow or microchip independent of the beam-to-flow angle.Doppler Optical Coherence Tomography (DOCT) is a noninvasive biomedical imaging method which can not only measure tissue perfusion but has the advantage of providing depth localized blood flow. However, three components of a velocity vector have not yet been measured with the fiber-based time-domain Vector DOCT.This thesis focuses on the development of Vector Doppler Optical Coherence tomography (DOCT), a novel non-invasive and quantitative technique using broadband near infrared light (1.3μm) for imaging and quantifying 3-D flow velocity in microcirculation.The thesis is divided into five parts.In the first part the basic principles principle of OCT and DOCT is introduced and the state of the art for developing a novel technology for quantifying vector flow velocity in microcirculation real-time and none invasively is discussed.In the second part two main velocity signal acquisition methods based on Doppler shift and Doppler bandwidth in OCT is described. Different signal processing in digital is introduced.In the third part, various methods of vector flow velocity based on OCT system is analyzed concretely. We proposed a novel DOCT system with phase-resolved algorithm to measure three components of an arbitrary velocity vector. A narrowband phase plate was inserted in the sampling arm of a Doppler optical coherence tomography system between the collimator and the focusing lens. The narrowband phase plate produced 3 independentΔk's(the average difference between the wave vectors of incoming and outgoing beams) after passing through the focusing lens. After calibration, an unknown velocity vector field inside a microtube can be quantified by solving a three-dimensional minimization problem.The fourth part the novel DOCT system was tested in a series of experiments with liquid flow phantom of known optical and flow characteristics. The experiments results of flow phantoms indicate that the proposed methods can estimate the 3-D vector velocity with an acceptable low bias and standard deviation.Finally, a conclusion of our work and the direction of further improvements are presented in the fifth chapter.