Research On The Application Of OCT In Fluid-flow Velocity Measurement

Many diseases are accompanied with changes in blood flow, therefore the measurement of blood flow is very important in clinical diagnosis and treatment. Optical coherence tomography(OCT) is a promising optical imaging method, with high resolution, high imaging speed and no destruction. Using OCT technology to measure flow velocity is an important aspect of the application of OCT. There are mainly three methods: Doppler OCT(DOCT), the flow velocity quantification using OCT with correlation, and optical angiography(OAG).This paper elaborates the mathematical principles of the three methods. DOCT calculates the Doppler shift and then gets the flow velocityaccording to Doppler principle. Velocity quantification using OCT with correlation alternately scans two close cross sections of the fluid to estimate the time interval for scattering particles to pass through the two sections, and then get the velocity of scattering particles. In OAG, the reference mirror is mounted on a piezo stage, and then through a series of data processing, the flow images and structureimages are separated.Then we compare the three methods and summarize theiradvantages and disadvantages. DOCT, especially phase-resolved DOCT, has a fast imaging speed and can be used in real-time imaging.But it’s very sensitive to environmental interference, and the flow directionis needed in the measurement. Velocity quantificationusing OCT with correlation does not depend on the flow direction, but it requires high resolutionand big cattering particles. OAG is not sensitive to environmental interference, and has a high imaging speed and SNR.But it can only isolate flow imagesfrom structureimages, but not measure the velocity magnitude.In the last part of this paper,we conducted experiments of DOCT and OAG. Firstly, we built an SD-OCT system and got two and three-dimensional structure images of human finger skin. Secondly, we used DOCT system to measure the flow velocity of a capillary-milk model and got DOCT three-dimensional flow image for the first time in our laboratory. Thirdly, we successfully built an OAG system and achieved OAG flow detection for the first time in our laboratory.