Study On Spatial Resolution Of One-Dimensional Magnetic Nanoparticle Imaging

Magnetic nanoparticle imaging as a new type of medical imaging technology with accurate resolution and real-time,and the most basic and most critical measure of image quality is the spatial resolution.In this thesis,the superparamagnetism of magnetic nanoparticle is used to generate nonlinear magnetization under the applied magnetic field,and then the imaging can be realized by combining Langevin function.Then the main factors influencing the spatial resolution are studied by simulation and experiment.Firstly,an one-dimensional magnetic nanoparticle imaging model is established.In the space,a dynamic excitation magnetic field and a DC gradient magnetic field are applied.The superposition magnetic field will produce a field-free point(FFP)which moves back and forth in one-dimension space.The response signal is obtained according to the superparamagnetic and saturation characteristics of the particles.In this thesis,an onedimensional reconstruction algorithm is used to realize imaging which maps the time-varying response signal to the spatial distribution of magnetic nanoparticles.Secondly,the image is rebuilded on the MATLAB simulation software,and the spatial resolution is analyzed according to the reconstructed image quality.According to Langevin function,the point spread function(PSF)restricts the spatial resolution,and the main factors are the DC gradient magnetic field and the particle size distribution of the magnetic nanoparticles.By comparing these two factors,it is found that the DC gradient magnetic field is bigger and the resolution is better.The particle size distribution of magnetic nanoparticles is logarithmic normal distribution.When the particle expected size in superparamagnetic particle size range is larger,the higher the resolution,the bigger the variance of particle size and the better the resolution.Finally,an one-dimensional magnetic nanoparticle imaging resolution test system is designed to verify the effect of DC gradient magnetic field and particle size distribution of magnetic nanoparticles on spatial resolution.The system mainly includes electromagnet to generate magnetic field,through the PID regulation to achieve a smooth output;two coil reverse series measurement signal;LABVIEW with MATLAB software to achieve data processing.The experimental results show that the influence of the DC gradient magnetic field and the particle size distribution of the magnetic nanoparticles on the spatial resolution is consistent with the theoretical simulation results.