The Coupled Multi-physical Field Analysis And Synthesis Of Magnetic Fluid Hyperthermia

The magnetic nanoparticles in AC alternating magnetic fields produce a large amount of heats according to the Neel relaxations.Based on that,a new promising approach,Magnetic Fluid Hyperthermia(MFH),is developed for tumor treatment.The temperature field distribution in the cancer has a significant influence on the therapeutic effect of MFH.As a result,it is generally required to maintain the temperature in a certain level(e.g.42～46℃ for complementary therapy,46～70℃ independent therapeutic and 70～90℃ thermal ablation).The temperature distribution is a key factor in MFH.Moreover,the magnetic intensity and the nanoparticles’ distribution in treatment region also play an important role in cancer therapy.In this regard,this dissertation is trying to comprehensively address some key issues for the analsyis and design of a MFH device,and the main works and findings are summarized as:1.The therapeutic effect of MFH depends on the proper temperature controlling of the cure region.As a result,the temperature uniformity of the treatment region and the temperature gradient of the boundary of the treatment region are chosed as two ojtective functions,and then a multi-objective optimization model is developed to analyze and synthese the multi-physical coupled field of Magnetic Fluid Hyperthermia.2.Through a thorough study of hyperthemia mechanism,a coupling multi-physical model,together with a sequential-coupling strategy,is developed.Firstly,Galerkin residual approach is used to develop the finite element discrete equation of time-harmonic electromagnetic and steady temperature fields.Secondly,a nonlinear iterative prcedure is proposed to solve the nonlinear temperature distribu which has a high nonlinearity because the heat generation has a complex relationship with the surrounding temperature.3.A multi-objective optimization algorithm,QPSO-DET,is proposed to optimize the temperature distribution of MFH.The numerical results on both mathematciall test function and applications demonstrate that the proposed algorithm has a better balance of the local and global search ability,and is a fesible and robust multiobjective optimizer.4.For improving the therapeutic effect of MFH,the volume fraction solid φ of the magnetic fluid are firstly chosen as the decision parameters,which lead to a more optimal temperature distribution.Considering the disconnective of the optimized φ along the border of adjacent elements,Radial Basis Function(RBF)interpolation method is employed to smooth the solid fractions of therapeutic region of MFH.The numerical result reveals that the temperature distribution after interpalation is almost identical to the original one.5.The Analysis and optimal design of a typical MFH system is conducted using the aforementioned theories and methods,and the available engineering conclusion are given.