Modeling of Transient Tissue Temperatures and Biotransport of Vasodilators During Localized Heating

Thermally induced large blood flow increases have been extensively observed in muscle. However, no one has attempted to study the physiological mechanisms that under these phenomena. If the mechanisms are fully understood, it may be possible to noninvasively, thermally control blood flow, thus controlling tissue temperature, during hyperthermia treatments. The present study applies a compartmental model of the pharmacokinetics/dynamics coupled with a one-dimensional Pennes bio-heat-transfer equation to study the local thermoregulation in tissue subjected to heating. Temperature responses to different applied power levels have been simulated. The simulations are seen to generate similar temperature profiles to those observed in the previous in vivo experiments. This implies that the coupled pharmacokinetic/dynamic and 1D energy balance models developed here capture the essence of the links between tissue temperature and blood flow oscillations and the activities of the vasoactive substances. Thus, it appears that such pharmacokinetic/dynamic models can provide a fundamental basis for coupling the tissue temperature distributions to blood flow oscillations—as opposed to using the ad hoc time delays used in the original investigations. Results from this study provide a promising, physiological basis for coupling blood flow increase with localized heating, which can be used as a guideline for the design of physiological experiments to identify the key vasoactive agents present during heating. In addition, once the key vasodilators are identified and the corresponding biochemical pathways are fully understood, research can then proceed to find a way to thermally control blood flow for the purpose of enhancing the efficacy of noninvasive thermal therapies.