Research On The Key Technology And Optimization Of Magnetic Temperature Measurement

Temperature is an extremely important process parameter in nature,including life activities.Magnetic nanothermometer is considered to be an effective remote temperature measurement solution for targets with a certain depth inside the object.In response to meet the needs of non-contact precise temperature imaging,the interaction between magnetic nanoparticles and the magnetostatic field is studied.As the inhomogeneity caused by magnetic nanoparticles can be detected by nuclear magnetic resonance technology,the concentration and temperature information of particles are transmitted through the magnetic resonance frequency and relaxation time of the hydrogen nucleus.In addition,based on the urgent need for rapid temperature measurement,the temperature model of magnetic relaxation under a mixing-frequency magnetic field is constructed.Considering that the existing magnetic temperature measurement technologies require the object to be measured to be magnetic transparent,which makes magnetic resonance temperature measurement unable to be used in some specific patients,such as carrying cardiac pacemaker,a method of magnetic nanoparticles temperature measurement for metal objects is proposed.The details are as follows:First of all,in order to deeply understand the magnetization model of magnetic particles and its influence on the parameters of magnetic resonance,this thesis selects the magnetofluid in the static magnetic field as the research object and analyzes the interaction between the magnetofluid and the excitation magnetic field.Based on the induced magnetic field produced by a single magnetic nanoparticle,considering the various interactions between particles and the magnetic field,the influence of magnetic fluid on the static magnetic field are analyzed by Monte Calro simulation.On this basis,the magnetofluids with different particle size and concentration are simulated to analyze the influence of these characteristic factors.This study provides a theoretical basis for the combination of magnetic nanoparticle temperature measurement technology and magnetic resonance technology.Secondly,by combining the magnetization model of magnetic nanoparticles with the resonance frequency and relaxation time in magnetic resonance,the model of solving magnetic nanoparticles magnetization and further obtaining the concentration and temperature information is proposed.The experimental results show that NMR technology can identify the concentration change of the magnetofluid,and the temperature measurement error can be less than 1K through resonance frequency and transverse relaxation time.In this study,magnetic resonance technology is used to solve the problem that the current magnetic nanoparticle temperature measurement technology can not directly realize the temperature imaging,which verifies the feasibility of combining the two methods for temperature imaging.However,the current magnetic resonance technology has a certain demand for time,which cannot meet the needs for the magnetic hyperthermia.The magnetic relaxation temperature measurement under mixing-frequency magnetic field is studied to improve the measurement speed.The relaxation model of magnetic nanoparticles under the mixingfrequency excitation field is constructed,and the phase deviation introduced by the hardware system in the phase measurement process is taken into account.As shown in the test results,the static temperature measurement error is less than 0.1k at high frequency,and the dynamic temperature measurement error is less than 0.2K.Finally,in order to break through the limitation that the magnetic temperature measurement requires the object to be measured to be magnetic transparent or not to carry metal,the non-invasive temperature measurement method of metal objects is explored.After analyzing the influence of the ferromagnetic objects on the magnetic nanothermometer,the inductance temperature change model with magnetic nanoparticles is constructed,so as to realize the remote temperature measurement of the external and internal temperature of the metal object.