A Study Of Optical Projection Tomography Based On Limited-angle Reconstruction

Optical Projection Tomography(OPT)technology is a three-dimensional imaging method.It uses the characteristic that light travels along a straight line in a transparent medium to collect projection images of the biological sample from different angles.Three-dimensional images of the sample can be obtained by tomographic reconstruction of these projection images.With the development of science and technology,OPT technology is moving toward high spatial resolution,dynamic imaging of living body,etc.For the dynamic imaging of living body,this thesis proposes a new type of sample fixation.The main research work of this thesis is:1.For the problem that the samples in the previous OPT could not survive or the survival time was too short,a new sample fixation method was used to perform OPT imaging.After anaesthetizing the sample in the culture dish,the dish was fixed under the turntable of the OPT system for imaging.Using this method can reduce the damage to the sample,so as to achieve OPT in vivo and dynamic observation.2.For the problem of low image quality reconstructed by iterative algorithm,a pixel vertex driving model is designed.The projection model projects the four vertices of the pixel along the direction of the light source to the detector.According to the position of the four vertices after the pixel is projected,which detectors are projected is determined,and then the area where the projection and the detector overlap is taken as the weight.Compared with the distance-driven model,the projection model has higher accuracy,and the quality of the reconstruction results is better when applied to the iterative reconstruction algorithm.3.The reconstruction algorithm used in this thesis is an algebraic reconstruction algorithm based on TV minimization.For the problem that the algorithm consumes more time,GPU acceleration is performed.The experimental results show that after the acceleration,the operating speed is increased by about 29 times.The algorithm is used for simulation experiments to explore the influence of different projection angle ranges on the quality of reconstruction results.The experimental results show that as the projection angle decreases from 180 degrees to 90 degrees,the overall quality of the reconstructed image will become worse and worse,but the image quality of the first quadrant remains basically unchanged.When the projection angle is greater than 110 degrees,the image quality in the center area also remains better.The image quality of the fourth quadrant will be significantly affected by the projection angle,and the image quality will decrease significantly as the projection angle decreases.4.The real data collected by the OPT system is used to explore the influence of different projection angle ranges on the reconstruction result,and it is confirmed that the minimum projection angle of practical application can be satisfied.The experimental results show that if you want to observe the very detailed information inside the sample,the projection angle should be at least 140 degrees to meet the requirements;if you want to observe the structure of the entire sample,the projection angle should be at least 110 degrees.Finally,a limited-angle OPT imaging was performed on tobacco roots,and the root hair density was clearly observed from the reconstruction result.