Research On Flow Measurement Based On Spectral Optical Coherence Tomography

Optical coherence tomography (OCT) as a new imaging technology, has caught many biomedical scientists’ attention due to its non-radiation, non-touch, high resolution and high sensitivity. Spectral Domain Optical Coherence Tomography (SDOCT) is a second-generation OCT technology, compared to the first generation Time Domain Optical Coherence Tomography (TDOCT), it has obvious advantages in terms of imaging speed, signal to noise ratio and sensitivity, and it has played an important role in ophthalmic imaging, small animal imaging and other fields. So it has broad clinical and research foreground.In this thesis the theory of SDOCT was introduced in the first character. The scattering process of light was qualitatively explained by the interaction between light and biological tissue. Analyzing the schematic of SDOCT, we pointed out the superiority of the SDOCT. The basic therories of the OCT imaging technology were introduced, including low coherence interference theory and cofocal microscopy theory. With analyzing the signal components of SDOCT, the effective signal and noise signal was pointed out. Then, the main parameters of the SDOCT imaging system were discussed.Secondly, high-speed high-resolution SDOCT system was constructed in our lab and its basic schematic was illustrated in detail. Based on2X2fiber coupler (50/50), we designed interference optical system. The X-Y scan of the system was performed by a2D optical scanning galvanometer which was controled by a DAQ card. The signal acquisition system was designed using an Ultra-fast line array CCD camera and an1145lines/mm grating. By a high speed IMAQ grabber, acquired spectrum was tranfered to the personal computer.A spectrum coordinate calibration method was adopted to compensate the dispersion of the system.Then, the method of calculation of the image was pointed out, and the selection of the light source was discussed.Finally, phase-resolved flow measurement experiments were performed using this SDOCT system. Combined with SDOCT and Doppler effect, the velocity of the flow particle was obtained from the calculation of the phase difference. The horizontal scan was selected through the theoretical analysis, and then the phase stability of the system was assessed.The generation mechanism of pattern noises and phase noises were analyzed, then a B-scan spectra average method and a double-pass compensation method were used to eliminate them, and acquired a satisfactory result. A constant phase was adoptted to eliminate phase wrapping, which doubled the velocity measurement range. Early stage Chicken embryo heart blood flow was measured in vivo, and the distribution of flow velocity was analyzed quantitatively.In summary, we builted a fast high-resolution SDOCT system and phase-resolved flow measurement experiments was performed.Our research realized short imaging time, high resolution and large flow measurement range SDOCT systerm, this played an advance role in the clinical applications.