Bioheat transfer in a branching countercurrent network during hyperthermia

Area of Science:

• Biomedical Engineering
• Thermodynamics
• Human Physiology

Background:

• Accurate modeling of bioheat transfer is crucial for understanding tissue thermal responses.
• Existing models like Pennes' equation offer simplicity but may not fully capture microcirculatory complexities.
• Thermoregulation significantly influences tissue temperature, especially during hyperthermic conditions.

Purpose of the Study:

• To develop and present a sophisticated bioheat transfer model for human extremities.
• To investigate spatial temperature variations in arterioles, venules, and muscle tissue.
• To incorporate thermoregulation of muscle blood flow during hyperthermia.

Main Methods:

• Utilized a two-parameter model by Baish et al. for microcirculation heat exchange.
• Incorporated thermoregulation of muscle blood flow into the bioheat model.
• Computed spatial temperature variations under resting and hyperthermic conditions.

Main Results:

• Mean tissue temperature did not equal the average of arteriole and venule blood temperatures, even with equal vessel radii.
• Tissue temperature profiles during hyperthermia closely matched predictions from the simpler Pennes bioheat transfer model.
• Thermoregulatory mechanisms in muscle were identified as a key factor for the observed model agreement.

Conclusions:

• The developed model provides detailed insights into bioheat transfer in human extremities.
• The influence of thermoregulation can make simpler bioheat models surprisingly accurate under hyperthermia.
• An "experimental" thermal conductivity was proposed to bridge theoretical findings with practical experimental estimations of perfusion effects.