Study Of Cell Light Scattering Based On Finite-Difference Time-Domain Method

Lives are made up of cells.The cells have an important influence on the activities of lives.In medical research and clinical diagnosis,many diseases are diagnosed and treated according to the cell morphology and internal conditions.In medical diagnostic technology,optical diagnostic technology has gradually become an important means of cell diagnosis because of its advantages of non-invasiveness,convenient and uncomplicated operation.When light propagates in tissues and cells,it is affected by the media and scatters.Light scattering is the main mode of light propagation in biological tissues.Cells light scattering images contain a wealth of information about cell size,morphology,and internal structure,and do not require bio-markers.Cell light scattering technology is non-invasive to biological tissues and cells and is gradually becoming an important field in optical technology.Most of the theoretical studies about light scattering images of cells rely on Mie scattering theory to establish cell models and simulate the light scattering patterns of cells.According to Mie scattering theory,cells must be regarded as homogeneous medium sphere,and as a result the complex structure inside the real cell can not be restored well.However,the finite difference time-domain method can break up the problem space into discrete grids and build more complex cell structures.The established models and simulated cell light scattering patterns are more in line with the actual situation and are gradually applied to cell light scattering simulation study.However,3D simulation based on the finite-difference time-domain method requires a large amount of calculation,and high hardware requirements.The two-dimensional cell models established in this paper greatly reduce the workload and compare results with experimental results,ensure the reliability of the results.In this thesis,we introduce the basic knowledge of light scattering of particles firstly,including light scattering,Maxwell' s equations and light scattering theory and method.The basic knowledge of the FDTD method is then highlighted,which is important for the subsequent simulation of cell light scattering.Firstly,the basic equations and Yee cellular theory of finite difference time-domain method are expounded.And then we introduce numerical stability and dispersion,absorption boundary conditions,near-far field conversion and other important knowledge points.After studying these basics,we started to simulate the light scattering of biological cells.After introducing the relevant knowledge of biological cells,the recursion formula of finite difference method in two-dimensional time domain is obtained,and next we perform the near and far field extrapolation in two-dimensional space,the parameters are set,the correctness of the procedure is verified.Light scattering patterns of two-dimensional biological cell models are simulated and the effects of different factors on cell light scattering are discussed.