Research On Imaging And Applied Current Thermoacoustic Imaging

Applied Current Thermo-acoustic Tomography(ACTAI)is a new technology for imaging the electrical conductivity of a target body.It has the advantages of high contrast in electrical impedance tomography and high spatial resolution in ultrasound imaging.ACTAI has high excitation efficiency and strong detection signal-to-noise ratio.It will have a broad application prospect in the field of bio-impedance.Firstly,the theoretical analysis and numerical simulation of the forward and inverse problems of ACTAI are carried out.In the study of forward problem,the control equations and boundary conditions of the three-dimensional model are given.The thermal function distribution of the target is simulated by the finite element method.According to the thermoacoustic wave equation,the thermoacoustic signal received by the ultrasonic probe is solved.The target acoustic source distribution is reconstructed from the acoustic signal received by ultrasonic probe by filtering back projection method.The simulation results provide a theoretical basis for the subsequent experiments.Secondly,a new method of electrical conductivity reconstruction based on generative adversarial network is proposed.By using Wiener filtering deconvolution method,the original acoustic fields on the detected boundary are reconstructed by the acoustic signals originated from the ultrasonic transducers.Then the initial acoustic source image is obtained by the filtering back projection method.The initial acoustic source image are used as training samples and labels of a deep learning network,which is designed for the conductivity reconstruction.This method can mine the inverse problem model contained in the data,and then reconstruct the high resolution conductivity image.The proposed new method provides a new idea for the reconstruction of conductivity in the injected current thermoacoustic imaging.Finally,the experimental system of ACTAI is designed and built,which comprises an excitation system capable of generating nanosecond high voltage pulse signal,a signal detection system capable of accurately capturing thermoacoustic data,and a data acquisition and imaging software system.Then,the experiments are carried out with sodium chloride gel phantom.The results show that the detected signal is consistent with the distribution of the electrical conductivity of the target,which verifies the feasibility of the ACTAI method.