Bioheat Transfer

Heat transfer in living tissues is a complicated process because it involves a combination of thermal conduction in tissues, convection and perfusion of blood, and metabolic heat production. Over the years, several mathematical models have been developed to describe heat transfer within living biological tissues. These models have been widely used in the analysis of hyperthermia in cancer treatment, laser surgery, cryosurgery, cryopreservation, thermal comfort, and many other applications. The most widely used bioheat model was introduced by Pennes in 1948. Pennes proposed a new simplified bioheat model to describe the effect of blood perfusion and metabolic heat generation on heat transfer within a living tissue. Since the landmark paper by Pennes (1948), his model has been widely used by many researchers for the analysis of bioheat transfer phenomena. And, also a large number of bioheat transfer models have been proposed to overcome the shortcomings of Pennes’ equation. These models include the continuum models which consider the thermal impact of all blood vessels as a global parameter and the vascular models which consider the thermal impact of each vessel individually. Although, several bioheat models have been developed in the recent years, the thermoregulatory control mechanisms of the human body such as shivering, regulatory sweating, vasodilation, and vasoconstriction have not been considered in these models. On the other hand, these mechanisms may significantly influence the thermal conditions of the human body. This causes a serious limitation in using the bioheat models for evaluating the human body thermal response. In order to remove this limitation, Zolfaghari and Maerefat (2010) developed a new Simplified Thermoregulatory Bioheat (STB) model based on the combination of the well-known Pennes’ equation and Gagge’s thermal comfort model. The present chapter aims at giving a concise introduction to bioheat transfer and the mathematical models for evaluating the heat transfer within biological tissues. This chapter is divided into six sections. The first section presents an introduction to the concept and history of bioheat transfer. The structure of living tissues with blood perfusion is described in section 2. Next, third section focuses on the mathematical modelling of heat transfer in living tissues. In the mentioned section, a brief description of some of the most important bioheat models (i.e. Pennes (1948) model, Wulff (1974) model, Klinger (1974) model, Chen and Holmes (1980) model and so on) is presented. Afterwards, section 4 explains the complexity of evaluating heat transfer within the tissues that thermally controlled by thermoregulatory mechanisms such as shivering, regulatory sweating, vasodilation, and