Spectral Domain Optical Coherence Tomography And The Application In Biomedicine

Optical Coherence Tomography is a new tomographic imaging technologydeveloped in1990s, which is obtaining the internal depth information of biologicaltissue through detecting the back scattering. OCT is composed by Michelsoninterferometer illuminated by broadband source. The low coherence of broadbandsource achieves the advantages of OCT, such as high resolution, non-contact,non-invasive, and so on. OCT is divided into time domain OCT (TDOCT) andfrequency domain OCT (FDOCT). Time domain OCT is a traditional OCTtechnology, which is through controlling the movement of reference mirror to realizethe axial scanning and obtain the depth information. Due to the scanning mode, thepicking rate of TDOCT is very slow, which is restricting the applications. Frequencydomain OCT is a new type OCT technology developing from TDOCT and is dividedinto spectral domain OCT (SDOCT) and swept source OCT (SSOCT). Spectraldomain OCT is detecting the interference spectrum of reference and sample light,which is realized the depth parallel sampling and improve the picking rate. Now,many fields are focus on the research of SDOCT.In the beginning, the paper introduces the basic principle of OCT and theimaging principle of SDOCT including the experimental system. SDOCT uses thespectrometer to detect the interference spectrum, and then obtain the depthinformation through Fourier transformation of interference spectrum, which is noneed of axial scanning.Allying with the2nd hospital of Tianjin medical university, we study the oraltissue (salivary glands) to detect the disease, which can be realized real-time imagingand is useful for the research of endoscope. Allying with Nankai university school ofmedicine and college of life science, we use SDOCT to study the zebrafish retinaldamage-regeneration caused by ultraviolet rays. Furthermore, the zebrafish areinjected with clodronate-liposome to study the regeneration process. In addition, weassess retinal light damage at various dpt (days post treatment) using immunohistochemistry in order to offer a solid criterion for an analytic result by OCT.The OCT results give a great agreement with the immunohistochemistry. Ascomparison, the SDOCT system is a real-time and non-invasive technology withoutfluorescence labeling and frozen cryosectioning. As a result, we observed the injuryand regeneration of the cone photoreceptors cells with SDOCT in live after UV lightillumination. The results demonstrate the SDOCT system for dynamic detection ofretina damage by UV illumination without requiring fluorescence labeling and frozencryosectioning, which gives a great value of the studying of the medicine of retinaldisease.In traditional optical system, the axial and transverse resolution areinterdependent, however, in OCT system the resolutions are independent. In OCTsystem, the axial resolution is determined by the bandwidth of broadband source; thetransverse resolution is determined by the NA of objective lens. In the commonobjective lens system, the transverse resolution and depth of focus (DOF) arereciprocal. The larger the resolution is, the shorter the DOF. In the paper, we design amicro-element named modified fractal zone plate to resolve the problem and give theexperimental results.To study the features of cancers, we extract the scattering coefficient of rectaltissue to quantify the disease from the OCT images allying with Nankai universityaffiliated hospital. In the paper, we use the data fitting method of OCT images toextract the scattering coefficient and confirm the disease. To give a criterion, wecompare the results with pathological sections which gives a perfect result.