Numerical Simulation Analysis Of Hyperthermia Temperature Field Of Magnetic Fluid Based On Nanoparticle With Low Curie Point

As an emerging tumor treatment technology,magnetic fluid hyperthermia has the advantages of good conformability and good tumor targeting.One of the major technical difficulties in its clinical application is the unsatisfied control of hyperthermia temperature.For the magnetic nanoparticles with low Curie point,when the temperature is close to Curie point,the heat generation capacity gradually decreases,which can automatically control temperature and prevent the overheating of the tumor,having great potential in clinical application.Numerical simulation is a common strategy in making the treatment plan of the magnetic fluid hyperthermia,which has the advantages of low cost and time saving.However,due to the unclear quantitative relationship between specific loss power(SLP)of magnetic nanoparticles with low Curie point and temperature(T),the corresponding thermal simulation is lacking.In this thesis,taking the magnetic nanoparticles with low Curie point developed by our research group as examples,the SLP-T relationships of the magnetic nanoparticles were established,and the temperature field in tumor during hyperthermia were simulated by finite element method,providing references for the hyperthermia application of the magnetic nanoparticles with low Curie point.The main contents are as follows:Firstly,the experimental platform of testing the magnetic thermal heating was established.The SLP-T relationships of magnetic nanoparticles with Curie point of 37.5℃,56.0℃ and 61.0℃were measured.The experiment results showed that,when the temperature is over 37℃(body temperature),the SLP of the three kinds of nanoparticles decreases significantly with the increase of temperature,and the nanoparticles with lower Curie point have more significant decrease.The hyperthermia model with nanoparticles evenly distributed in the tumor was established.The SLP-T relationships were applied to the temperature field simulations.The results showed that,when the volume of the magnetic fluid is fixed,the nanoparticles with lower Curie point require higher mass concentration to elevate the maximum temperature in tumor to the upper limit of modest thermotherapy temperature(46℃).But they can acquire faster temperature rise in the tumor and larger thermal dose within the same period of time.Secondly,according to the form of metal cells,the multi-point injection strategies of magnetic fluid,which imitate the body-centered cubic(BCC),face-centered cubic(FCC)and hexagonal close-packed(HCP)were proposed.With the effective treatment volume under modest thermotherapy(42℃-46℃)as the evaluation criteria,the effects of the distribution of magnetic fluid and the distance among the injection points on the tumor temperature field were studied.The results showed that,the multi-point injection of magnetic fluid can significantly reduce the heating accumulation and uneven problem of the temperature field,increasing the effective treatment volume.For the multi-point injection,the gathering of heat can be evacuated by increasing the space among different injection points,reducing the over-heated tumor volume.The effective treatment volume can be increased by enlarging the magnetic nanoparticle mass around the tumor edge.In the injection strategy of imitating BCC,when the volume ratio of the magnetic fluid around the tumor edge over all the magnetic fluid in the tumor is larger,the effective treatment volume is bigger.Finally,the tumor model with blood vessel was established.The effects of blood vessel position and radius on the hyperthermia temperature field were studied.The results showed that,when the blood vessel locates in the healthy tissue outside of the tumor,the heat dissipation caused by the blood has marginal effect on the temperature field.When the blood vessel is in the tumor,the blood in the vessel dissipates the hyperthermia heat,causing 1.6℃-4.6℃decrease in the highest temperature of the tumor,compared without blood vessel.While the radius of blood vessel changes from 1.5 mm to 2.5 mm,the highest temperature in the tumor drops by 3.7℃-4.7℃.Besides,through solving the flow field by Brinkman and continuity equations,and solving the concentration field by free diffusion and convective diffusion models,the influence of the nanoparticle diffusion on the hyperthermia temperature field was studied.The results showed that,the diffusion of the nanoparticle causes the decrease of the temperature in the tumor,reducing the effective treatment volume.