| Optical coherence tomography(OCT) was developed in 1990 s as a novel optical imaging method with several advantages, including non-invasive, non-destructive, real-time imaging, high resolution and high sensitivity. Compared with the first generation OCT--time domain(TD-OCT), the second generation OCT--Fourier domain OCT(FD-OCT) has great advantages, i.e. high sensitivity and signal-to-noise ratio(SNR).With the development of technologies, functional extensions of traditional OCT have been put forward. Such novel modalities include Doppler OCT, Polarization-Sensitive OCT and Molecular contrast OCT, etc. Among them, Doppler OCT is the combination of Doppler effect and OCT technology, which can not only offer high-resolution structural images of biological samples, but also provide hemodynamic information of blood vessels. It is well known that blood vessels keeping growing during tumor formation; study on vascular distribution attracts lots of interests in tumor research field. In this dissertation, we have set up a spectral domain Doppler optical coherence tomography system for imaging the nude mouse model with dorsal skin window chamber. The main contents are summarized as following:1. We have introduced the general situation and classification of optical coherence tomography; the principle and development of Spectral domain OCT(SD-OCT) and functional extensions of OCT.2. The Doppler effect, the principle and development of Doppler optical coherence tomography have been briefly introduced; A comparison has been made between two algorithms of optical Doppler tomography, i.e. short time Fourier transform(STFT) and based on phase-resolved in terms of spatial resolution and imaging scale.3. Based on the principles of Spectral domain OCT, we have theoretically analyzed the factors which affect the resolution, imaging depth, signal-to-noise ratio and scanning rate of SD-OCT system. Optical components with optimal performance have been selected. We then built a spectral domain Doppler optical coherence tomography system. Axial resolution, transverse resolution and imaging depth of the SD-OCT are 6.84μm, 8.18μm and 2.58 mm, respectively. The spectral resolution(sampling resolution) of the rapid spectrometer is 0.0674 nm with the axial scanning rate of 29 k Hz. Experiments on pearls and jades have been performed with the SD-OCT system, and the results showed that this system has high spatial resolution and can provide images of the sample with fine structures. Moreover, the SD-OCT system was used in detecting the liquid flow rate in tubes, imitated blood flow, which demonstrated its ability in studying vascular distribution and flow velocity of animal models in vivo. Next, we used this system to obtain images of the blood vessels inside the dorsal skin window chamber of the nude mouse and gained clear distribution images of these blood vessels. These results have provided an effective method for studying the changes of blood vessels in the process of tumor growth.4. The performance of the SD-OCT system was further optimized. The line-scan CCD in the old system was replaced by a CMOS camera based on rapid spectrometer with higher scanning rate of 140 k Hz. In addition, the focal length of the focusing lens in the sample arm is changed to 30 mm. Compared with the original SD-OCT system, both the transverse resolution and penetration depth have been improved. By imaging the same type of mouse model, the vascular distribution images with higher resolution have been received.The SD-OCT developed in this dissertation has the advantages of high imaging speed, high spatial resolution, and can be used to image the distribution of blood vessels and measure the blood flow, which holds great potentials for basic research in animal tumor model. |
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