Research On Catheter-based PS-OCT System And Polarization Demodulation Methods

Catheter-based polarization sensitive optical coherence tomography is the catheter-based OCT function expansion and evolution.Compared with common catheter-based OCT,catheter-based PS-OCT can provide more abundant tissue information of vascular wall and various plaques,and get more obvious polarization contrast patterns caused by birefringence.However,the existing catheter-based PS-OCT system is not perfect in overcoming the changes of polarization parameters caused by the rotation of catheter optical fiber,polarization injection and extraction,polarization demodulation methods and so on,which limits its clinical application.In this paper,we begin with several difficult problems that limit the clinical application of PS-OCT,including the system device of catheter-based PS-OCT,the method of polarization injection and extraction,the method of polarization demodulation and the fiber optic catheter of distributed biochemical sensor,etc.The design scheme of PS-OCT system based on catheter,the method of polarization calculation and the preliminary exploration of distributed biochemical sensor optical fiber catheter are proposed.The system construction,theoretical analysis and experimental verification are completed.The design scheme of PS-OCT system based on catheter,the method of polarization calculation and the preliminary exploration of distributed biochemical sensor optical fiber catheter are proposed.The system construction,theoretical analysis and experimental verification are completed.In detail,this paper has completed those parts:1.Study on the polarization demodulation method of the catheter-based PS-OCT system.By using the polar decomposition of Mueller matrix and constructing similar matrix,we present a new polarization determination method,similar Mueller matrix(SMM)method,for the catheter-based PS-OCT system to eliminate the diattenuation and depolarization effects and realize the polarization demodulation of the tissue birefringence.Based on the statistical characteristics of linear birefringence in polarization mode dispersion(PMD),a two-state numerical dispersion compensation method is proposed to correct the dispersion of PS-OCT system.By correlation operation is used to realize the registration of four polarization states.2.Research on catheter-based PS-OCT system.A polarization-sensitive OCT imaging system based on high-speed rotating optical fiber imaging catheter is designed and built,including the construction of improved all-fiber Mach-Zehnder interferometer,the generation and control of dual-input polarization state,rotating mechanism and imaging catheter control.Complete the software development of PS-OCT system,realize the optical path calibration,data acquisition and image reconstruction.The tissue birefringence imaging experiment was completed,the polarization demodulation of samples was carried out,and the phase retardance imaging for sample with high contrast was output.3.Explore the optical fiber catheter combined with distributed biochemical sensing and imaging.The possibility of combining catheter-based OCT with OFDR technology is preliminarily explored,and the concept of fiber catheter combining distributed biochemical sensing and imaging with tapered fiber as the sensing component at the front of the fiber catheter was proposed.The distributed sensing principle based on OFDR tapered fiber is studied.The distributed refractive index sensing experiment of tapered fiber is completed on the OFDR system.The distributed sensing ability is verified,which lays a foundation for the development of distributed biochemical sensing and imaging combined with optical fiber conduit.