The Response Of Skin And Tumor Under Hyperthermia Based On Fractional Thermoelasticity

Laser technology are widely used in medical treatment.For example,laser ablation increases the temperature of human tissues to a certain stage,causing irreversible damage to diseased tissues and leading to the apoptosis of cancer cell.To increase the rate of hyperthermia elimination in diseased tissue while minimizing the effect on normal tissue surrounding it,it is necessary to investigate the thermoelastic response of biological tissue when disturbed by the high speed and high intensity laser heat source.Because the laser heating process will produce a large instantaneous temperature difference in biological tissue,the resulting huge heat flow and the temperature gradient will make the heat conduction in the tissue take the form of abnormal diffusion.However,the classical Fourier heat conduction model assumes that the heat transfer velocity is infinite,which is incompatible with the reality of this transient problem.Therefore,a fractional thermoelastic model that can describe the non-Fourier effect and anomalous diffusion of thermal conduction in biological tissue is established in this dissertation to solve the thermoelastic response of skin and breast tumor tissues under laser heating.Furthermore,the physical meaning of the parameters in the generalized heat conduction model and the influence of fractional order differentiation are analyzed.The fractional order thermoelastic model proposed in this dissertation is compared with the existing generalized thermoelastic model.Finally,the effects of individual factors are considered,such as blood perfusion rate.Additionally,the effect of the laser beam’s moving speed within the tissue is considered during percutaneous laser thermal ablation surgery.The main works in the dissertation are shown as follows:(1)The application of current optical heating technologies in medicine is discussed,as well as the mechanical flaws of current optical thermal therapy research in terms of temperature and deformation control.The methods for describing thermoelastic problems and fractional derivatives are introduced in detail and simply classified,and the gaps in current theoretical model research are discussed.(2)On the basis of the Pennes bioheat energy conservation equation and the dual-phase-lag heat conduct theory,a generalized biological heat transfer model based on the Caputo fractional order differential is established,as well as a time fractional order generalized bio-thermoelastic model in combination with the Duhamel-Neumann equation.(3)The thermoelastic responses of a skin tissue with finite length under a boundary sudden loading are solved by time fractional generalized bio-thermoelastic model.The effects of blood perfusion rate in skin tissue are analyzed,and the effects of relaxation time and fractional factor in the model are discussed.(4)The one-dimensional thermoelastic problem of breast tumor tissue stimulated by an embedded mobile laser heat source was solved by using the time-fractional generalized thermoelastic model.The temperature,elastic displacement,and stress responses of the tumor are solved,and the effect of the moving speed of the heat source on the thermoelastic response is investigated.