Research On Experimental System Of Magnetoacoustic Magnetic Nanoparticles Concentration Imaging

Magnetoacoustic magnetic nanoparticles concentration imaging is a multi-physics imaging method based on the coupling effect of magnetic and acoustic fields,which has the advantage of high-resolution acoustic imaging.In order to further promote this imaging technology to the practical application of clinical medicine,it stimulates its huge potential application value.This thesis studies the experimental system of magnetoacoustic magnetic nanoparticles concentration imaging.First,studies the forward problems of imaging,and analyzes the basic principles of magnetoacoustic magnetic nanoparticles concentration imaging.The physical process from the magnetic field force of the magnetic nanoparticles in the magnetoacoustic magnetic nanoparticles concentration imaging system to the generation of the magneto acoustic signal is theoretically analyzed.Through the establishment of a two-dimensional axisymmetric simulation model of magnetic nanoparticle clusters and biological tissues,the effects of different current excitation signals and external magnetic field gradients on the magnetic field force of magnetic nanoparticles,as well as the effects of different nanoparticle concentrations and nanoparticle cluster shapes on the sound pressure signal.The results show that the magnetic force density has a quadratic positive correlation with the external magnetic field gradient;the concentration has a positive correlation with the magnitude of the magnetoacoustic signal.In addition,it is verified that the sound pressure signal is affected by the number and shape of magnetic nanoparticle clusters.Based on the analysis of the magnetic field force experienced by the magnetic nanoparticles,it is further proposed to use a Multiple coils structure to provide excitation for the magnetoacoustic magnetic nanoparticles concentration imaging system to achieve a lower current excitation to generate a time-varying magnetic field with a stronger external magnetic field gradient and a higher uniformity.The parameter optimization of the excitation current of the Multiple coils is carried out by the beetle antennae search algorithm,and the magnetic field gradient of 0.3T/m is the design goal.And use the simulation model established by COMSOL to compare the uniformity and uniform area of the gradient magnetic field generated by the Multiple coils and Maxwell coils.The comparison results show that the magnetic force of the magnetic nanoparticles in the Multiple coils structure,is more uniform than that of the Maxwell coils,and the uniformity area is larger,which proves the feasibility of the Multiple coils structure to reduce the current excitation and optimize the uniformity of the magnetic field.Finally,the experimental system of Magnetoacoustic magnetic particle concentration imaging was designed.Based on the principle of capacitor charging and discharging,FPGA was used as the control part to provide the pulse signal with the width of 0.5?s?2?s and the amplitude of 3.3V.The amplitude of the pulse excitation source was adjustable from 0 to 800 V,and the whole imaging experimental system was built.Copper ring,iron sheet and iron ring were used as the experimental targets.Through the analysis of magnetoacoustic signal collected,the results showed that magnetoacoustic imaging technology could detect the boundary information of copper ring and ferromagnetic material in space,and with the increase of the radius of copper ring,the peak value of sound pressure signal collected by ultrasonic transducer decreased gradually,which verified the feasibility of the experimental system and imaging method.The research results can promote the clinical application of magnetoacoustic magnetic nanoparticles concentration imaging and provide a reference for optimizing the imaging effects of this imaging method and other imaging technologies.The thesis has 55 pictures,5 tables,and 82 references.