Study Of Near-infrared Confocal Microendoscopy

Cancer is a major disease that threatens human health.Among various cancers,the proportion of digestive tract cancers have been in the first place for many years.Studies have demonstrated that early diagnosis can greatly improve the cure rate of cancer.Therefore,researches on medical equipment that can be used for early diagnosis of cancer have also become hot topics.As an advanced technology,confocal microendoscopy that excited by 488 nm laser is outstanding in the field of disease diagnosis in digestive tract.This confocal microendoscopy can provide the cellular resolution in vivo real-time without biopsy,and it characterized by high contrast and high speed imaging.Therefore,it is favored by doctors and patients.However,confocal microendoscopy with visible exciting light still meets great challenges in deep tissue imaging.First of all,visible light is easily scattered in biological tissues due to its short wavelength,which makes it difficult to stimulate fluorescent markers in deep tissues.Secondly,because of the scattering,signal-to-noise ratio(SNR)will decrease with the increase of imaging depth,which seriously affects the imaging quality.To solve the above problems and realize deep tissue imaging in digestive tract with high resolution,this paper studied the optical fiber bundle based confocal microscopy,labeling methods with different wavelengths and imaging in digestive tract of mouse.On this foundation,we present an optical fiber bundle based near-infrared confocal microendoscopy system and apply it to study structure characteristics of tissues at different depths in digestive tract when excited by visible light and near-infrared light.Finally,the near-infrared confocal microendoscopy was further used for the diagnosis of ulcerative colitis.The main contents of this paper are as follows:Firstly,theoretical simulation,device selection and system optimization.Based on the theoretical analysis and combined with the measurements of the absorption coefficient and scattering coefficient of mice,we simulate the propagation of different wavelengths in tissues of mouse by Monte Carlo Simulation,demonstrating that the near-infrared light has a stronger penetration than the visible light in the biological tissues.Combined with clinical available fluorescent markers,a laser source with 785 nm wavelength was selected.In order to meet the high requirements of the end face of the optical fiber bundle in the imaging process,a variety of Lapping films were used to grind the end face of the optical fiber bundle.Based on this study,a near-infrared confocal microendoscopy system was built.According to the features of fluorescence in the imaging process,we studied the condenser lens and confirmed the 25 ?m pinhole according to 20 ?m diameter of Airy disk of condenser lens,optimizing the SNR of the system.Through the measurement and analysis of various optical properties of optical fiber bundle,a software of image processing has been developed.Secondly,parameters testing and tissue imaging.By designing and processing miniature objective and making optical fiber probe,the performance of the system was effectively improved.Combined with the new optical fiber probe,the main parameters of the system were measured,showing that the system has a good imaging resolution with 1.55 ?m.The field of view,working distance and imaging speed are 330 ?m,300 ?m and 5 fps,respectively.Combined with the imaging results of the 488 nm confocal microendoscopy system and near-infrared tissue imaging,we demonstrate that the near-infrared confocal microendoscopy system has a higher contrast than the visible system.On the basis of previous studies,the labeling methods have been preliminarily explored by using the fluorescent markers.Thirdly,deep tissue imaging and disease diagnosis.Various features of mouse esophagus at different depths demonstrate the advantage of deep tissue imaging in near-infrared confocal microendoscopy system.On this basis,by establishing the model of ulcerative colitis in mice,we obtained the structures at different depths of mouse colon with ulcerative colitis,demonstrating that the near-infrared confocal microendoscopy system is an effective method for disease diagnosis in digestive tract.In a word,we have developed a near-infrared confocal microendoscopy that can observe the structures of tissues at depth of 300 ?m with cellular resolution in real-time.