The Study On Full-field Optical Angiography Functional Imaging Technique

Full-field optical angiography is an emerging angiography method with high temporal and spatial resolution.It is suitable for real-time imaging in vivo.It has a good clinical application prospect and has been widely used in retina,zebrafish and mice.This thesis,achieved full-field optical angiography functional image,mainly studies the full-field optical angiography imaging method and angiography debounce algorithm,the large depth-of-field full-field optical angiography imaging method based on contrast pyramid fusion algorithm,the measurement method of absolute transverse blood flow velocity,and the blood oxygenation imaging method.The specific work is as follows:1)Study on full-field optical angiography imaging methodThe thesis proposes a new imaging method combining full-field optical angiography based on intensity fluctuation modulation effect with sub-pixel matching based on normalized cross-correlation,which solves the problem of blurring the full-field optical angiography image caused by external factors or biological samples due to respiratory heartbeat.Experimental analysis shows that this method can solves the problem of blurring the whole field optical angiography image caused by external factors or biological samples due to respiratory heartbeat,and improves the image quality.2)Study on the Large depth-of-field full-field optical angiographyIn the full-field optical angiography imaging method,there is a common shortcoming.Only the vascular information of the plane in the depth of field can be obtained.To solve the problem of defocus caused by the surface and thickness non-uniformity of the biological sample,this thesis proposes a large depth-of-field full-field optical angiography imaging method base on contrast pyramid fusion.By using 10 full-field optical angiography images under different focal planes for fusion,the depth-of-field of the imaging system can be extended more than three times.3)Study on full-field optical blood flow velocity measurementIn this thesis,a method for obtaining the absolute transverse blood flow velocity in vessel centerline is proposed.The blood vessel image is extracted based on the fuzzy connection segmentation algorithm,and the centerline of the blood vessel is extracted by topology method.Finally,cross-correlation analysis is performed using the vessel centerline image and the instantaneous modulated depth sequence images of the blood flow to obtain the absolute transverse blood flow velocity in vessel centerline.In this paper,the absolute transverse blood flow velocity was measured by the blood vessel of the chicken embryo in 5 days old.It was verified that the method can accurately measure the absolute transverse blood flow velocity in vessel centerline.The method proposed in this thesis is helpful to study the role of blood flow velocity in the pathogenesis of vascular diseases such as anemia,thrombosis and retinopathy.4)Study on full-field optical oxygen imagingIn this thesis,the full-field optical measurement method is used to image and measure the blood oxygen content of biological tissues.Since the light absorption coefficient of Hb O₂ is smaller than the light absorption coefficient of Hb at the wavelength of 785 nm,the light absorption coefficient of both is opposite at the wavelength of 830 nm.Their wavelength path difference is not significant（<6%）,and the error in blood oxygen content imaging due to wavelength path differences can be ignored.On this basis,the full-field optical angiography technique was used to image and measure the blood oxygen content.In this thesis,the dual-wavelength laser is used to replace the single-wavelength laser as the imaging source of the experimental system.The simulation of the blood oxygen content of the human arteriovenous vein is carried out with different concentrations of red and blue ink mixed solution.The method achieves blood oxygenation and its concentration measurement.