Synchrotron Radiation Infrared Microspectroscopic Tomography And Its Application

With the needs of scientific research and production,infrared spectroscopy has become one of the most important analytical methods widely used in materials science,archaeology,biochemistry and medicine.Infrared spectroscopy can obtain the spatial spectral information of a substance through the reaction of infrared light with the substance molecule.However,the laboratory infrared light source is difficult to collect the microregion information of samples because of its low brightness.Therefore,this greatly limits the study of the key information affecting the performance of these samples.Synchrotron infrared light has the advantages of small point size,high collimation and high brightness.Using the synchrotron infrared light as the source of the infrared spectrometer can easily focus to the diffraction limit and still obtain the synchrotron radiation infrared（SRIR）spectrum with high signal-to-noise ratio.Therefore,synchrotron radiation infrared spectroscopy can achieve the spatial resolution of the micron level,and obtain the spectral information that difficult to be collected by the globar infrared light source in the microscopic field,so as to measure the tiny changes in the sample.The point scanning synchrotron radiation infrared 3D microspectroscopy is a non-destructive technique.It is based on synchrotron infrared spectroscopy and collects the 3D infrared microspectra of samples by the way of point scanning.Then the 3D spatial distribution of the components of the sample was reconstructed by the reconstruction algorithm.The point scanning synchrotron radiation infrared 3D microspectroscopy easily overcome the problem of overlapping projection information and the inability to distinguish the characteristic peaks of the samples which are very close to each other.Therefore,the spectral information of any point in the internal structure of the sample under test can be obtained by this technology.Besides,this technology can conduct qualitative and quantitative analysis of the reconstructed material,and observe or analyze the 3D space from multiple angles and in an all-round way,which helps human better understand the microscopic physical and chemical mechanism of the sample.This paper introduces the principle the point scanning synchrotron radiation infrared 3D microspectroscopy and its reconstruction algorithm which includes analytical algorithm and statistical iterative algorithm.The analytical algorithm is Filtered back-projection（FBP）algorithm,and the statistical iterative algorithm includes Ordered-subset expectation maximization（OSEM）algorithm,Penalized maximum likelihood algorithm with weighted linear and quadratic penalties（PML-Hybrid）,and Ordered-subset penalized maximum likelihood algorithm with quadratic penalties（OSPML-Quad）.FBP algorithm requires the complete angle projection data,while the statistical iterative algorithm does not.In this paper,MiTeGen loop,mouse oocyte and pinnule were used as reconstruction samples to analyze the results that analytical algorithm and statistical iteration algorithm reconstructed the components of the sample.In the first chapter,we introduce the principle and application of infrared spectroscopy,and then focus on the synchrotron radiation infrared microspectroscopy as well as the 3D infrared spectroscopy and briefly describes the research background.In view of the limitation of the present 3D infrared spectroscopy,we propose the point scanning synchrotron radiation infrared 3D microspectroscopy.The second chapter is The Principle of Synchrotron Radiation Infrared CT Microspectroscopy.We detailly introduce the principle of the point scanning synchrotron radiation infrared 3D microspectroscopy and briefly describe the reconstruction algorithm′s principle,while include its advantages and disadvantages.In the second part,we use the MiTeGen loop as sample,and reconstruct its amideⅡ(1490 cm^-1)by the OSPML-Quad algorithm as well as analyzes amideⅡ′s 3D spatial distribution.At the end of this chapter,we analyze the results that the FBP algorithm,OSEM algorithm,the PML-Hybrid algorithm and OSPML-Quad algorithm reconstructed MiTeGen’s amideⅡrespectively.The third chapter is Study and Application of Synchrotron Radiation Infrared CT Microspectroscopy Optimization in Biomaterials.In the first part,we discuss mouse oocyte’s synchrotron radiation infrared spectra and its nucleic acid,amideⅠ,lipids and amide A synchrotron radiation infrared mapping.Then,the nucleic acid′s 3D spatial structure is reconstructed by algorithms which included FBP algorithm,OSEM algorithm and PML-Hybrid algorithm.We analyze and compare their reconstruction results of the nucleic acid.At last,we use PML-Hybrid algorithm to reconstruction mouse oocyte’s amideⅠ,lipid and amide A because of its better performance.In the second part,we select turtledove pinnule as sample and discuss its synchrotron radiation infrared spectra as well as pinnule’s amideⅡ,amideⅠ,lipid,amide A synchrotron radiation infrared mapping.We use the FBP algorithm to reconstruct pinnule’s amideⅠwith complete angle projection data.On the contrary,the reconstruction of amideⅠis incomplete angle projection data with OSEM algorithm and PML-Hybrid algorithm,while OSEM algorithm and PML-Hybrid algorithm are under the optimal number iterations.According to analyze the reconstruction results of that three algorithms,we reconstruct pinnule’s amideⅡ,lipid and amide A by PML-Hybrid algorithm that is under the iteration number of 4.The last chapter is Summary and Prospect.In this chapter,the research contents and results of in the paper are summarized,and the shortcomings and future research directions of the point scanning synchrotron radiation infrared 3D microspectroscopy are proposed.