Research On Method And Application Of Acoustic Detection Based Multi-Physics Coupling Imaging

As a hybrid imaging method,acoustic detection based multi-physics coupling imaging follows the basic principle that pathological characteristics of the human body are highly related to its physical properties in different physical filed.Acoustic wave is used to extract the pathological information of human body by multi-physics coupling mechanism.The high resolution of ultrasound imaging and the high contrast of physical properties in different physical fields are achieved simultaneously by those acoustic detection based multi-physics coupling imagings,including magenetoacoustic tomography(MAT),thermoacoustic imaging(TAI),photoacoustic imaging(PAI)and X-ray induced acoustic computed tomography(XACT).Huge attentions were drawn in past decades for their non-invasive and selective.Here,we will discuss the methods and applications of MAT,XACT and PAI.By using magnetic filed to induce acoustic wave,magnetoacoustic coupling imaging can extracts the electrical impedance,which reflects the pathological state of the tissue.A finite difference time domain method(FDTD)based theoretical mode and algorithm were proposed to investigate the basic principle of MAT in acoustical nonuniform media.The forward problem was solved by considering the refraction and reflection during the propagation of acoustic wave;while,the acoustic source was reconstructed with the acoustic property,which was estimated from the correlation between signals acquired by transducer in symmetrical position.The performance of proposed algorithm was evaluated by simulation study and phantom experiment.This method provides a solution for the forward problem and inverse problem of acoustic nonuniformity in MAT.The distribution of acoustic characteristics obtained in the reconstruction process provides additional structural information for MAT while realizing conductivity based functional imaging.In XACT,which using X-ray as the excitation source,the absorded dose can be obtained through the acoustic signals induced by X-ray.The feasibility of XACT in dosimetry was first investigated with its physical principle.A XACT system,which combine a clinical linear accelerator(LINAC)and signal element transducer,was developed to investigate the feasibility and accuracy of XACT in radiotherapy dose measurement.Compare with the radiochromic films,the accuracy of XACT dose resolution,which is lower than the maximum clinically acceptable error,was first achieved in soft tissue.A clinically relevant LINAC parameter and soft tissue phantom were involved in experiment study,and the relative dose maps of soft tissue was first obtained by XACT during radiation therapy.To further investigate the clinical translation of the XACT,a dual-modality imaging system was adapted from a clinical available commercial ultrasound platform with 0.33 mm ultrasound spatial resolution and 1.3 mm XACT spatial resolution.Real-time monitoring the misalignment between the X-ray field and target was achieved with ultrasound frame rate 20.6 and XACT frame rate 0.15.The use of this dual-modality imaging system provides a new solution for image guided radiation therapy.In PAI,which using the nano-scecond laser to induce acoustic wave,the acoustic signals can express the optical absorption rate.An integrated multi-modality imaging system,which combine photoacoustic microscopy(PAM),optical coherence tomography(OCT)and fluorescence microscopy(FM),were developed for ocular imaging.To achieve the potential clinical translation,system is designed for big animal eye,and the laser energy involved in this system is lower than ANSI safety limit.High resolution multi-modality imaging was first achieved in both albino and pigmented rabbit with retinal neovascularization.The results demonstrate that the multimodality imaging system can noninvasively visualize retinal neovascularization,and verify the leakage of neovascularization using FM and fluorescein dye.The results demonstrated the feasibility of integrate image system in diagnosis of blood vessel related disease,which shows the potential clinical translation of this technology.In summary,this paper presents a description of the method and application of acoustic detection based multi-physics coupling imaging,including MAT,XACT,PAM.Different characteristics of biological tissue were extracted from detected acoustic wave throught multi-physics coupling imaging with different excitation sources.In MAT,it provides the solution for the theoretical mode with acoustical uniformity,and shows the possibility of MAT to achieve structural imaging and functional imaging simultaneously.In XACT,a relative dose map of soft tissue was achieved during radiation therapy,and the establishment of real-time dual-modality imaging has potential application in image guided radiation therapy.In the application of PAM,high resolution retinal neovacuarization images in big animal eye were acquired by the integrated multi-modality imaging system.