Experimental Study Of Continuous Wave Diffuse Optical Tomography System Based On LED Light Source

Nowadays,as people pay more and more attention to their health,medical imaging technology has developed rapidly.In current clinical applications,Magnetic Resonance Imaging(MRI),Ultrasonic(US),Computed Tomography(CT)and other technologies occupy the mainstream,but these methods have certain defects in safety,portability and comfort.Diffuse optical tomography(DOT)is an optical molecular imaging technique based on the optical properties of normal tissues and cancerous tissues,and the internal images of tissues can be obtained by inverse algorithm.As a new imaging method,diffuse optical tomography is widely used in breast imaging,brain imaging,epilepsy diagnosis,etc.Most of the existing diffuse optical tomography systems use laser as the light source.This study mainly uses the Light Emitting Diode(LED)instead of the laser as the system Light source to explore the imaging capability of the system.The main purpose of this study is to build a continuous wave diffuse optical tomography system with LED as the light source,and design a new interface,so that the system is not limited to the imaging of a single shape,and finally through a series of phantom experiments to verify the imaging capability and wide applicability of the system.The main work content is as follows:1.The theoretical basis of diffuse optical tomography is introduced.Firstly,based on the theory of optics,several main modes of action of light and biological tissues are expounded,and the important optical parameters are explained.Then the transmission theory of light in biological tissue is discussed: radiation transmission equation.The diffusion equations of three system modes are introduced.The diffusion equation in the continuous wave domain is introduced in detail.Based on this equation,the diffuse optical tomography algorithm using finite element method is described,and the forward and inverse problems in the algorithm process are explained in detail.2.Design and build a continuous wave diffuse optical tomography system based on LED light source.At the hardware level,a diffuse optical tomography system in continuous wave domain is constructed by using LED as the excitation light source and photodiode as the detector.A new interface is designed,which can be applied to the imaging of arbitrary shape object.In addition,a 3D scanner is used to obtain the information to build a 3D finite element grid.At the software level,the function of LabVIEW program is summarized,and the control flow of LED lighting by LabVIEW program through Field programmable gate array(FPGA)control card and the trigger of data acquisition card are introduced in detail.The algorithm is written to calibrate and align the 3D coordinates obtained by 3D scanner,and the software is used to generate 3D finite element mesh.Write MATLAB program to implement the experimental data preprocessing and generate the algorithm configuration file.3.The imaging capability of the system was verified by a large number of phantom experiments.The selection basis and production process of the phantom used in the experiment are introduced.A variety of interfaces are designed and a variety of shape phantom experiments are carried out.For cylindrical phantoms,32*32 light source-detector array was used to design experiments with different amounts,depth,sizes and contrast of target phantoms to verify the imaging performance of the system.On this basis,the phantom experiment of human brain was carried out,and a 40*40 light source-detector array was used.Through this experiment,the applicability of the system to objects of different shapes was proved.The system construction was successfully completed in this study,and the applicability of LED light source in the continuous wave diffuse optical tomography system and the wide applicability of the interface designed in this paper were proved by phantom experiments.