Research On The Magnetocaloric Effect And Application Of Microscaled Ferromagnetic Implant In Magnetically Mediated Hyperthermia

Magnetically mediated hyperthermia is a novel technology for cancer treatment.Based on the magnetocaloric effect of ferromagnetic implant in alternating magnetic field,ferromagnetic biomaterials were administered within the tumor site under alternating magnetic field to form a conformal high temperature zone,thus leading to a direct killing of tumor tissue without hurting the neighboring normal tissue.Arterial embolization hyperthermia is a combined technology of magnetically mediated hyperthermia and transcatheter arterial embolization for the treatment of hepatic carcinoma and renal carcinoma.Selective arterial embolization of tumors with ferromagnetic implants stops the hepatic arterial system from supplying blood to liver tumor,and the following exposure to alternating magnetic field further generate heating of the tumor tissues.This research focuses on novel microscaled ferromagnetic implant for arterial embolization hyperthermia,including design and implementation of the experiment platform as well as preparation process,characterization,magnetocaloric effect mechanism and thermal field distribution of the novel microscaled ferromagnetic implant.The main contributions of this thesis are summarized as follows.(1)Design and implementation of the optimized coil-type experiment platform for magnetically mediated hyperthermia.By optimizing the excitation coil,power supply circuit,resonant circuit and control system,the prototype for both big animal experiment and clinical trials were developed,thus setting up the experiment platform for magnetically mediated hyperthermia.The magnetic intensity,frequency and effective treatment area all meet the experimental requirements and exceed similar equipment.(2)Established the preparation process of ferromagnetic hollow microspheres based on the method of gas atomization.Ferromagnetic hollow microspheres were prepared based on the commonly use d gas atomization method in industry.The internal holes of these hollow microspheres were resulted by gas turbulence during the atomization process.Screening of physical properties followed to filter out qualified microspheres.(3)Verified the applicability and superiority of ferromagnetic hollow microspheres in arterial embolization hyperthermia.Based on the characterization and measurement of thermal power density,the ferromagnetic hollow microspheres were proven to be perfect implant for arterial embolization hyperthermia,better than other existing embolization medium in terms of heating efficiency,suspension performance and cost of production.(4)Established the theoretical model of heat production resulted from magnetocaloric effect for both hollow and solid ferromagnetic microspheres.Based on theories of ferromagnetism and electromagnetism,through theoretical derivation and multiphysics simulation,the theoretical calculation method of thermal power density of both hollow and solid ferromagnetic microspheres in alternating magnetic field was derived,followed by discussion in its applicable scope and parameter dependency.(5)Established the hyperthermia model of the ferromagnetic microspheres.Based on heat transfer theory and numerical calculation method,the numerical calculation model of temperature distribution with ferromagnetic microspheres as the heat source was established.The theoretical non-stationary temperature distribution was simulated using this model.Hyperthermia experiment with anthropomorphic phantom was carried out and verified the model.The main contributions of this research include(1)implementation of the optimized coil-type experiment platform for magnetically mediated hyperthermia;(2)establishing the preparation process of ferromagnetic hollow microspheres,and verifying the applicability and superiority of these microspheres in arterial embolization hyperthermia;(3)establishing the theoretical model of heat production and hyperthermia model for ferromagnetic microspheres.