Research On Numerical Simulation Of Combined Endoscopic Magneto-photo-acoustic Images

Pulse-echo ultrasound(US)imaging can provide the structural and anatomical information of biological tissues or organs.Photoacoustic tomography(PAT)and magnetoacoustic tomography with magnetic induction(MAT-MI)functional imaging have the ability to assess the changes of tissue component and function.Generally,a single imaging modaltiy can not describe the structure and function of biological tissues thoroughly.Hybrid multi-modality imaging integrating US,PAT and MAT-MI allows simultaneous US,PAT or MAT-MI and combines the high resolution of optical absorption with the high resolution and sensitivity of magnetoacoustic detection for deep detection.The location and component of pathological tissues can be accurately detected with the multimodal imaging.Furthermore,in comparison with the external detection,the endoscopic detection may be a better choice for the biological tubular structures,such as digestive tract,intestinal tract and blood vessel,through the body's natural openings or the minimally invasive incision.Endoscopic magneto-photo-acoustic(EMPA)combining magneto-photo-acoustic(MPA)imaging with endoscopic detection techniques can effectively observe and diagnose the biological tubular structures.This dissertation addresses the modelling and numerical simulation of EMPA imaging.Firstly,the ultrasonic echoes reflected or scattered by the multi-layered wall tissues,PA signals generated by the tissues illuminated by the short laser pulse and MA signal generated by the tissues placed in a static and pulsed excitation magnetic field are simulated.Then,the propagation and time-sharing acquisition of the ultrasonic echoes,PA and MA waves by an ultrasonic transducer mounted on the tip of the imaging catheter is simulated.Finally,the three types of raw ultrasonic signals are fused with an adaptive weighted fusion algorithm to obtain dual-mode or three-mode images.The validity of the method has been demonstrated with computer-simulated phantoms including tube-like phantom and coronary vessel phantom.The experimental results indicated that in comparison with a single imaging modality,combined imaging has the advantages of the single imaging method,and can provide more detailed structural and functional information of the target tissues.