Research On Multimodal Imaging Technology Based On Optical Coherence Tomography

The study of the connection between retina and brain and the study of "gut-brain axis" can facilitate the diagnosis of neurodegenerative diseases.Optical coherence tomography(OCT),as a non-invasive,high-resolution and real-time imaging technique for the retina and the gut,can be used for the study of the connection between retinal and neurodegenerative diseases and the "gut-brain axis".Mice,which are genetically similar to humans and are easy to reproduce,are ideal experimental subjects for such research.At present,commercially available OCT systems are mostly used for human imaging,which are not suitable for imaging mice.Therefore,this thesis aims to develop and build new multimodal imaging systems based on optical coherence tomography for the imaging of mice,to study the connection between retina and neurodegenerative diseases and the "gut-brain axis".The specific content of this thesis is as follows:(1)OCT-OCTA imaging technology for mouse retinaThe thickness of different layers of retina and the changes of blood vessels are potential markers to evaluate the progression of neurodegenerative diseases.In this thesis,a imaging technique combining OCT and OCTA for mouse retina was developed.The imaging system was designed according to the pupil size and input pupil power of the mouse and so on.In order to better image the mouse’s retina,three types of sample arms were designed and simulated,followed by the construction and debugging of the system,and finally the key parameters of the imaging system were measured.OCT and OCTA images were obtained by developing appropriate data processing methods.The performance of the three sample arms was evaluated by comparing the OCT and OCTA imaging results of the mouse’s retina in vivo,and the system was optimized according to the retinal imaging results.The axial resolution of the system in airs was 8.3 μm,the theoretical value of lateral resolution in mouse’s retina was 9 μm,the imaging depth in air was 6 mm,while in mouse eye was 4.44 mm,and the sensitivity was above 93 d B.Based on the imaging system,layers of mouse retina in B-scan images can be clearly seen,and the large blood vessels and optic nerve heads in the retina of mice can also be observed from the en face image and OCTA image.These results demonstrated that the proposed imaging system can be potentially used for mouse retina monitoring to study the connection between retinal and neurodegenerative diseases.(2)Multimodal endoscopic OCT and fluorescence imaging technique for mouse colonImaging the gastrointestinal tract(GI)to study the "gut-brain axis" may facilitate the diagnosis of neurodegenerative diseases.OCT and fluorescence imaging each has their own unique advantages.The combination of OCT and fluorescence imaging can simultaneously acquire morphological and molecular information of intestinal tissue.In this thesis,a multimodal endoscopic OCT and fluorescence imaging system for mouse colon was developed.In order to test the OCT system’s performance,an in vitro OCT imaging system was firstly designed and simulated,and the system was constructed and tested,and the key parameters were measured.The axial resolution of the in vitro OCT imaging system in air was 14 μm,the lateral resolution was 31.25 μm,and the sensitivity was 106 d B,and the imaging depth in air was 8 mm.An in vivo OCT imaging system was subsequently designed,which is suitable for imaging the mouse colon in vivo,and the designed probe was simulated with Zemax.By evaluating the simulation results,the probe with an theoretical lateral resolution of 23 μm and 30.8 μm was selected for fabrication.The optical transmittance of the customized probe was measured to be higher than 90%,and it can enable future in vivo imaging.