Study Of Bio-Heat Transfer For Some Practical Applications

Bio-heat transfer is a rising subject branch of the biomedical engineering intercrossed with a good many fields such as the biology, thermal physics and clinical medicine etc, whose core is to seek and make use of,one of the basic vital characters,the law of the matter and energy transmission.Mathematical model is very important to the study of Bio-heat transfer, and it is also the common foundation for both of the theoretical research and practical application. A successful model is the key to explain the mechanism of heat transfer in bio-tissue or between it and the environment, and is also the key to determine and indicate the temperature field in an organism. Since Pennes bio-heat transfer equation is published in 1948, researchers on bio-heat transfer put forward many models. Although all the models have a very limited range of applicability, there are still great ideas and experience among them. In regard to some special adjusting method of body temperature, such as perspiration, there is no present model could describe the behavior of perspiration in mechanism. According to how it is intense, or whether there exist sweat beads or sweat film in liquid on the surface of skin or not, we could separate the perspiration into concealed and revealed perspiration. With the compare and analysis about the subsistent bio-heat transfer models, the thesis divides the limb into layers according to its biological structure and its thermal characteristic by absorbing the helpful thought among those models. Considering the number of the existing sweat glands in skin layer is so great, we could take the skin layer as a kind of porous media in macro scale. Thus we use the flow and heat transfer theory of porous media to describe the perspiration in mechanism. Darcy's law is adopted to the model. Under the combined effect of mass equation, momentum equation and energy equation, we could obtain all the process of the flow and phase-change of sweat in sweat gland. The process of perspiration is affected by the environment conditions greatly, at the same time; the process will also be affected by the open situation of sweat glands. As a special adjusting method of body temperature, the perspiration could decrease the temperature of skin surface to about 1～20C, which will be helpful to maintain the body temperature steady.Hyperthermia is a treatment to heal the cancer by heating. That is, when some kind of physical energy is deposited into the bio-tissue, the thermal effect occurs and increases the temperature of bio-tissue to a fairly high temperature. When the process lasts for some time the cancer will shrink or even be cleared up, while the normal tissue will not be damaged. Since hyperthermia brings the patient small injury and high curative effect, when it is used with other therapeutic methods synchronously, hyperthermia will increase the curative effect of others greatly; hyperthermia has been a widely applicable method to treat cancer and is called "green therapeutics". The physiology mechanism of hyperthermia is the normal bio-tissue could survive under a high temperature but the cancer cells will be destroyed thoroughly at the same temperature. The selective kill of temperature is the basis of cancer hyperthermia. The key of the hyperthermia is the heating technology. How to heat the bio-tissue to a effective therapeutic high temperature (41～430C) and try not to harm the normal tissue is the most important thing to increase the curative effect. As the purpose, the accurate indication of temperature in cancer tissue during the process of hyperthermia is very important. Nowadays, people often use laser, microwave or supersonic as the heating source. The transport and being absorbed of the energy from outside is the only reason that heat energy is produced inside the tissue. When the heat is transferred in the tissue, the temperature of bio-tissue will arise. The thesis discusses the temperature response of bio-tissue when laser or microwave is introduced into the hyperthermia, and draws some conclusion useful...