| Magnetic induction hyperthermia is a branch of tumor thermotherapy,in order to induce apoptosis of tumor cells,magnetic induction hyperthermia takes advantage of the characteristic of heat generation of magnetic medium implanted in the tumor tissue when the alternating magnetic field is applied.Magnetic induction hyperthermia has obvious advantages,such as minimally invasive,targeted effect,and joint therapy,so it has become a focus research in tumor therapy at home and abroad.In this thesis,we established magnetic fluid hyperthermia?MFH?model about liver cancer of rat using the finite element software COMSOL based on the linear response theory.By means of the analysis of four kinds of magnetic medium within relaxation mechanism,such as Fe3O4?FeCo?fccFePt and L10FePt,we studied the influence about the change of magnetic medium parameters on dissipation power and temperature field,respectively.At the same time,the optimization method for the parameters of several magnetic medium is proposed.By increasing the dissipation power of the magnetic medium as much as possible,the dose of magnetic medium used in the treatment can be reduced,meanwhile,the adverse effects on surrounding health tissues of tumor will be minimized.The conclusion of this thesis can provide reference for magnetic medium preparation applied to magnetic fluid hyperthermia.Firstly,the types and characteristics of magnetic medium used in magnetic induction hyperthermia are briefly introduced,the heat generation theory of magnetic medium under uniform alternating magnetic field is mainly analyzed,the formula for power loss is derived as well.At last,the coupling principle of magnetic field and temperature field are introduced.Secondly,the numerical calculation method and the finite element simulation software are introduced,the biological tissue and magnetic medium parameters are given,and the numerical model about the process of magnetic induction hyperthermia based on the treatment of rat liver cancer is established,including geometric models and electromagnetic models.In the end,the Multi-physics coupling problem is solved by the finite element software COMSOL.Finally,the magnetic field parameters and magnetic medium parameters that affect the loss power of magnetic medium are analyzed,respectively.By analyzing the magnetic field parameters that affect the power loss,it is found that under the safety criterion of magnetic induction hyperthermia for biological tissue H0·f=5×109 A/?m·s?,there is an optimal value of magnetic field strength and magnetic field frequency,and the optimal values is corresponding to the type of the magnetic medium.By analyzing the parameters of magnetic medium that affect the power loss,it is found that there is an optimal effective relaxation time for the determined alternating magnetic field frequency.When the frequency is equal to 100 kHz,the corresponding optimal effective relaxation time is 1.59×10-6 s.For the determined magnetic medium type,when the effective relaxation time is equal to the optimal effective time,the loss power increases with the increase of the magnetic medium radius and eventually tends to be stable.Based on the theory we have discovered,an optimization method of magnetic medium parameters for magnetic induction hyperthermia is proposed in this thesis.By optimizing the parameters of the dominant relaxation,letting the effective relaxation time is equal to the optimal effective relaxation time obtained by theoretical analysis,the loss power of magnetic medium can be effectively improved.Through multiple injection,the uniformity of the temperature field in the tumor tissue can be increased.The more injection points,the lower temperature is in the center of the tumor,The temperature difference between the center of the tumor and the edge of the tumor also decreases,that is,the uniformity gradually increases. |
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