Bioheat transfer

In this chapter we start with fundamental aspects of local blood tissue thermal interaction. Discussions on how the blood effect is modeled then follow. Different approaches to theoretically modeling the blood flow in the tissue are shown. In particular the assumptions and validity of several widely used continuum bioheat transfer equations are evaluated. Different techniques to measure temperature, thermophysical properties, and blood flow are then described. The final part of the chapter focuses on one of the medical applications of heat transfer, hyperthermia treatment for tumors. 

The most important aspect of the bioheat transfer analysis by Weinbaum and coinvestigators was the identification of the importance of countercurrent heat transfer between closely spaced, paired arteries and veins. The countercurrent heat exchange mechanism, if dominant, was suggested as an eneigy conservation means since it provides a direct heat transfer path between the vessels. It was observed that virtually all the thermally significant vessels (>50 fan in diameter) in the skeletal muscle were closely juxtaposed artery-vein pairs (Weinbaum et al., 1984). Thermal equilibration in... 

Pennes Bioheat Transfer Model. It is known that one of the primary functions of blood flow in a biological system is its ability to heat or cool the tissue, depending on the relative local tissue temperature. The existence of a temperature difference between the blood and tissue is taken as evidence of its function to remove or release heat. On the basis of this speculation, Pennes [Pennes, 1948] proposed his famous bioheat transfer model, which is called Pennes bioheat equation. Pennes suggested that the effect of blood flow in the tissue be modeled as as heat source or sink term added to the traditional heat conduction equation. The Pennes bioheat equation is given by... 

Temperature Pulse Decay (TPD) Technique. Temperature pulse decay (TPD) technique is based on the approach described and developed by Arkin, Chen, and Holmes [Arkins et al., 1986 1987], This method needs no insulation, in contrast to some of the methods described above, since testing times are short, usually on the order of seconds. However, the determination of the thermal conductivity or the blood flow rate requires the solution of the transient bioheat transfer equation. 

Typically, the Pennes bioheat transfer equation is used to predict the temperature transient. It is assumed fiiat the thermistor bead is small enough to be considered a point source inserted into the center of an infinitively large medium. The governing equation and initial condition for this thermal process are described as... 

Temperature Pulse Decay Technique. As described in Sec. 2.4 under Temperature Pulse Decay (TPD) Technique, local blood perfusion rate can be derived from the comparison between the dieoretically predicted and experimentally measured temperature decay of a thermistor bead probe. The details of the measurement mechanism have been described in that section. The temperature pulse decay technique has been used to measure the in vivo blood perfusion rates of different physical or physiological conditions in varimis tissues (Xu et al., 1991 1998). The advantages of this technique are that it is fast and induces little trauma. Using the Pennes bioheat transfer equation, the intrinsic thermal conductivity and blood perfusion rate can be simultaneously measured. In some of the applications, a two-parameter least-square residual fit was first performed to obtain the intrinsic therm conductivity of the tissue. This calculated value of thermal conductivity was then used to perform a one-parameter curve fit for the TPD measurements to obtain the local blood perfusion... 

Crezee, J., and Lagendijk, J. J. W., 1990, Experimental Verification of Bioheat Transfer Themies Measurement of Temperature Profiles Around Large Artificial Vessels in Perfused Tissue, Phys. Med. Biol., 35(7) 905-923. 

Provides more detailed examples in bioheat transfer and pharmacokinetics which may be useful in modeling heat and mass transfer in the brain parenchyma. 

Chato, J.C., Fundamentals of bioheat transfer, in Thermal Dosimetry and Treatment Planning, M. Gautherie, Ed., 1990, Springer-Verlag New York, pp. 1 56. 

Chamy, C.K., Mathematical models of bioheat transfer, in Bioengineering Heat Transfer Advances in Heat Transfer,Y.. Cho, Ed., 1992, Academic Press Boston, pp. 19-155. 

Charny, C.K. and R.L. Levin, Bioheat transfer in a branching countercurrent network during hyperthermia. /. Biomech. Eng., 1989, 111 263-270. 

Incropera, F. P. and D. P. DeWitt. 2006. Fundamentals of Heat and Mass Transfer, 6th ed. New York John Wiley Sons. Provides the basics of heat and mass transfer. This edition includes areas of current interest such as fuel cells and alternative energy devices, electronics cooling, microscale heat transfer, and biological as well as bioheat transfer. Contains an extensive collection of new, revised, updated examples and homework problems illustrating real life engineering processes. 

Zhu et al. [61] developed a cylindrical geometry testing apparatus which incorporates a novel bioheat transfer model to test flame resistant fabric used in fire fighters protective wear. In the geometry test, heat flows from the radiant source, to the surface of the fabric and then through the fabric. It then flows through in air gap to the surface of a skin simulant. The rise in temperature on the surface of the skin simulant is used to determine the heat flux. This data is then applied to the thermal wave model of bioheat transfer, introduced by Liu et al. [62], the general form of which is ... 

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