The Numerical Simulation Of The Cryosurgery Process Basing On Arm Layered Model With Major Blood Vessels

Cryogenics and cryobiology are a discipline that has gradually developed along with the development of biology,medicine and cryogenic refrigeration technology.It is an important application of bioheat transfer in medical field.Cryosurgery invasive treatment of tumors has the advantages of small wounds,simple operation and better killing effect.The purpose of cryosurgery is to inactivate all tumor cells completely while minimizing the damage to normal healthy tissues around the tumor tissue.This is also the purpose of the optimal design of the cryogenic treatment process.This paper establishes the human arm model close to the actual situation,and simulates the steady and transient situations in temperature and stress fields.Conducting research and analysis on different simulation results:(1)Basing on the tissue structure of the human arm in regional anatomy,a new three-dimensional thermal model of the human arm with the major artery and veins is built.The arm model is divided into four layers due to the difference of physical parameters.This paper describes the specific heat and the coefficient of thermal conductivity as the linear function of temperature and set up the influence of dependent blood perfusion rate and metabolic heat generation on temperature and the major blood vessels flowing during the biological tissue heat transfer of the cryosurgical process.By this work the accuracy of numerical simulation is improved.(2)Liquid nitrogen(76K)as a freezing medium,numerical simulation of the temperature field of the model is studied.The steady-state temperature distribution of the tissue freezing process and the ice ball radius after the tissue freezing when the cold source is located at five different positions are obtained.It is important to judge the effective radius of the cold knife.Comparing the results of simulated calculations that whether consider the temperature dependence of blood perfusion and metabolic heat production or not.Proving that ignoring the temperature dependence of the two will make the temperature of the tissue be overestimated,ice ball diameter be underestimated.Exploring the impact of blood flow in major blood vessels on the temperature field inside the tissue.These work provide a theoretical basis for the treatment of disorders in the human arm.(3)This paper takes normal body temperature as the initial condition and apply a constant temperature cold source to perform transient analysis of changes in tissue temperature field.And it simulates the situation of different reheating modes and different reheating rates under the same mode.Through the monitoring of the reheating temperature changes at different locations,analyzing the changes of temperature field and treatment effects in the reheating temperature cycle under different conditions.(4)The stress of the simulation results is studied.The temperature field of model in freezing and process is added as a body load to the units,and the initial conditions and corresponding constraints are applied to the thermal stress coupled numerical simulation.This paper analyses the changes of total stress and stress in different directions and summaries the factors influencing the stress.