Research On Limited View Magnetoacoustic Tomography With Magnetic Induction Reconstruction Methods

Magnetoacoustic Tomography with Magnetic Induction(MAT-MI)is an ideal,attractive and promising new imaging modality for effective early detection and functional imaging of tissue lesions.The technology combines the electromagnetic technology,ultrasound and imaging technology,how long detection and imaging technology,both non-invasive,good contrast,high sensitivity and so on.MAT-MI uses a magnetic field and sound field coupling mechanism,through the external electromagnetic field excitation signal,the electrical characteristics of tissue information into sound signals to detect,and then rebuild the acoustic signal to achieve electrical characteristics of imaging.In this paper,the limited view MAT-MI reconstruction method is proposed to solve the problem that the finite element angle scan data is used to reconstruct the sound source and the electrical conductivity under the limited scanning angle.The imperfection,effective scanning angle and reliable conductance rate reconstruction of the minimum amount of data required to improve the reconstruction of magnetic induction imaging accuracy.Different biological tissues have different acoustical characteristics,the change of sonic velocity leads to the blurring and displacement of reconstructed images.In view of this phenomenon,we study the influence of acoustic heterogeneity on MAT-MI.The main work of this paper includes the following aspects:1.The research background and significance of this subject are introduced.The current research status of the existing magnetoacoustic imaging in China and abroad are summarized.The key problems to be solved are pointed out.The main research contents and innovations of this dissertation are described in detail.2.The MAT-MI is the problem of simulation and analysis.The uniform acoustic media concentric spherical model is established.The generalized finite element method is used to calculate the positive problem of the model.The eddy current under time-varying magnetic field is analyzed.The sound source generated under the static magnetic field is calculated and the sound source is calculated.The generated sound pressure curve,different radius,different position,different target tumor tissue model parameters have a greater impact on the distribution of sound pressure.3.With different model concentric sphere as the imaging target,the MAT-MI inverse problem of finite angle is solved.In this dissertation,the basic idea of fast split Bregman method is analyzed in detail.Auxiliary variables and equality constraints are introduced to solve the problem alternately and iteratively through quadratic optimization,image restoration and contraction operator.The algorithm was used to solve the problem of reconstruction of the sound source and the electrical conductivity of the limited perspective scan data,and to investigate the reconstruction of the sound source and the electrical conductivity of the tumor models with different radii,locations and doses under different scanning visual angles,Error analysis of the reconstruction results.4.The traditional time inversion method is improved,and the influence of acoustic heterogeneity on inductive magneto-acoustic imaging is analyzed by this method.The initial sound source is reconstructed by the time inversion of uniform medium,the initial sound source distribution is partitioned according to the prior information of acoustic features,and the final acoustic anisotropy sound source image is formed by the acoustic parameters of each area.The acoustic velocity,sound source and conductivity of acoustic inhomogeneous media are reconstructed by improved time inversions.The algorithm is compared with the traditional time-based inversion method.The results show that the improved time-inversion method can improve the acoustics Non-uniform MAT-MI for image reconstruction.5.The experimental platform of MAT-MI is built,the analysis and realization of each functional module of the experiment platform is completed,the MAT-MI software system based on LabVIEW is designed,the gel model with different electrical parameters and acoustic parameters is made,Gel simulation model experiment,the sound pressure signal was collected,the sound source and conductivity were reconstructed,and the error analysis of the reconstructed result was carried out.The experimental results are in good agreement with the simulation results,which proves that the inductive magneto-acoustic imaging The effectiveness of the system.In this paper,a new method for detecting the electrical properties of tissue has been studied.The research work will help to promote the application of inductive magneto-acoustic imaging to clinical applications,which has great scientific significance and practical value.