Development Of Spectral Domain Optical Coherence Tomography And Its Applications In Ophthalmology

As a non-invasive,high-resolution and high-sensitivity imaging modality,optical coherence tomography(OCT)is a powful biomedical optical imaging technique.Spectral domain OCT(SD-OCT)is an advanced OCT technique that capable of producing high-resolution cross-sectional and three-dimensional images,and capturing tissue motions and deformations with picometer-to-nanometer scale sensitivity in real time.SD-OCT has been widely used in biomedical research,especially in ophthalmology.In this thesis,we focus on the study of SD-OCT and its applications in ophthalmology.The main works are summarized as follows:1.A fiber-based SD-OCT system with high resolution(?4.3?m),long image-depth(?7.56mm)and fast line scan rate(-70kHz)is built.This system is capable of performing the real timeimaging of biomedical samples in vivo.2.A depth-enhanced SD-OCT based on the method of optical path encoding is proposed.A dichroic mirror is used to obtain two interference spectrums corresponding to two different imaging signals in one shot.Meanwhile,the interference signals would be captured by one photodetector and processed synchronously.It's an economical and stable technique to enhance the imaging depth of OCT.Full range complex SD-OCT without additional phase shifters is applied to expand the system imaging depth to?15.12mm.Cross-sectional images of anterior segment(including the crystalline lens)of human eyes as well as the whole mouse eyes are captured in vivo.3.Application studies in ophthalmology are carried out based on the custom-built SD-OCT system.Distortions in raw OCT images are calibrated by ray tracing algorithm.Eye accommodation in both healthy eyes and eyes with Implantable Collamer Lens(ICL)are investigated.The experiment results are coincidence with the accommodation theory of Helmholtz.Hydration of the mouse eye is studied.The results indicate that hydration has close relationship with dry eyes,cataract and glaucoma.The process of lens-induced myopia in mice is monitored and assessed by OCT.4.Phase-sensitive SD-OCT is developed and used to measuring the ocular pulse in the anterior chamber in vivo.An optimized scanning protocol is introduced.Bulk motions and environmental vibrations are compensated.A high sensitivity of 0.9?m/s minimal velocity is demonstrated at a wide detection band of 0 to 380 Hz.The experiment results indicate that the relative motions are most likely caused by respiration and heartbeat.5.To improve the resolution of OCT,the technology of optical super-resolution is adopted.A three-zone annular phase filter is demonstrated and inserted in the sample arm.In the proposed probe of a spectral domain OCT system,the width of the central lobe of the axial intensity point spread function is apodized by the filter to be within the coherence gate determined by the light source,while its side lobes are lying outside the coherence gate without contributing to the coherence imaging.As a result,an improvement of about 20%in axial resolution is confirmed.