Digital Enhancement Of Motion Contrast In Label-free OCT Angiography And Its Applications In Tracking And Detection Of Rat Photothrobosis

As a way of biomedical imaging,Optical Coherence Tomography(OCT)has outstanding advantages of high resolution,high sensitivity,high speed and non-invasiveness,which plays an important role in the field of medical imaging.Fourier Domain OCT(FD-OCT),which is currently the major part of OCT imaging technology,enables three-dimensional(3D)imaging of structure of tissue with high resolution.However,for the aim of seeking more contrast mechanism to meet the need of disease’s early diagnosis and treatment,functional OCT has become a new function extension of OCT.OCT angiography(Angio-OCT)is one of typical functional OCT.Combining 3D imaging ability of OCT and movement recognition ability of dynamic scattering technique,Angio-OCT enables label-free 3D vascular imaging with the ability of capillary detection,which has wide applications in the field of basic scientific research,clinical disease diagnosis and treatment.The research work of this paper is mainly focused on Angio-OCT imaging technology.Through formula derivation and theoretical analysis,the imaging algorithm of Angio-OCT and its classification error rate are stated.On this basis,research on motion-contrast enhancement of Angio-OCT is conducted.Besides,combining Angio-OCT with the photothrobosis model,study on longitudinal in vivo intrinsic optical imaging in the rat photothrobosis model is carried out.According to the statistical model analysis,there exists a residual overlap area between statistical distribution of static tissue beds and dynamic flow signals.When it comes to threshold segmentation for blood flow signal extraction,classification error rate(CER)is inevitable,resulting in the decrease of motion contrast.In order to reduce CER for high motion contrast angiography,a method of component compounding in wavelet domain is proposed.Both flow phantom and live animal experiments are performed.Meanwhile,quantitative analysis is done by using CER.The results show that the angiogram has an improved motion contrast and a better vessel connectivity and CER decreases by 83%and 71%respectively after component compounding in wavelet domain.Furthermore,the research on longitudinal in vivo intrinsic optical imaging of cortical perfusion and cellular damage in the rat photothrobosis model is conducted with the optical imaging method of Angio-OCT.With the help of photothrobosis model,ischemic stroke model can be simulated.The whole dynamic process(15 days)of vessel distribution before and after photothrombosis formation as well as recovery is clearly showed for the first time.Besides,a clear presentation of the dynamic changes of blood vessel distribution during the process of photothrombosis formation(30min)is achieved.At the same time,quantitative analysis on the photothrobosis model is done,including vessel area density,fractal dimension and attenuation coefficient.The research may be beneficial to the pathological analysis and drug development and effectiveness evaluation of thrombus.