Photoacoustic Tomography Based On Filtered Back Projection Algorithm

Optical acoustic tomography(PAT)is a new nondestructive testing technology which combines pure optical imaging with pure acoustic imaging.The technology is to reconstruct the acquired signals by using pulse laser as the excitation source and the photo acoustic signal as the information carrier,and realize the structure and function imaging of biological tissue,which has the advantages of high contrast and high resolution.Filter back projection algorithm is one of the image reconstruction algorithms.The low frequency part will be distorted due to vibration(that is,artifacts will occur).How to reduce the artifact and improve the image quality is the focus of this paper.This paper mainly studies the filter back projection algorithm,and the main research contents and results are as follows:(1)The theoretical research and simulation analysis of the photoacoustic pressure signal are carried out.The sound pressure is related to the initial photo acoustic pressure.Under the condition of constant pulse intensity,the optical absorption coefficient will affect the initial sound pressure.The difference of photo acoustic imaging is actually the difference of optical absorption coefficient,and the light-sound pressure intensity and optical absorption coefficient are linear.(2)The filter back projection algorithm is studied.In the filter back projection algorithm,RAM LAK filter is selected to analyze the reconstruction results of the image,and the reasons for the artifacts are analyzed.Finally,it is found that when the image is reconstructed by the filter back projection algorithm,the image produces less artifacts and higher quality.(3)In order to solve the problem of artifact in reconstruction,Hilbert converter is applied to the back projection reconstruction,and the comparison is made with the filtering back projection algorithm using ram LAK filter.The experimental results show that the reconstruction image obtained by Hilbert converter has smaller mean square error,higher peak signal-to-noise ratio and higher reconstruction quality.(4)The factors influencing imaging quality were studied.In the process of image reconstruction,sampling angle,whether interpolation or not,detection points will affect the reconstruction quality of the image.Through simulation and comparative analysis and considering the time and cost,we can get high precision results when the total angle sampling,interpolation and detection point number are 125,and the reconstruction image is clearer.