Radiofrequency capacitive heaters: the effect of coupling medium resistivity on power absorption along a mouse leg

A capacitive radiofrequency source in conjunction with a temperature-controlled electromagnetic coupling medium has the potential of delivering uniform heating distributions in a mouse leg for experimental studies to investigate the use of hyperthermia as a treatment for cancer. The system has been adopted by a number of groups who have confirmed that uniform temperatures can be achieved in the presence of blood flow along a one-dimensional line which extends between the plates across the leg. In this paper, a simple mathematical model is presented and verified experimentally to demonstrate that parallel-plate capacitive radiofrequency heaters produce an inherent absorbed power distribution along the leg which is determined by the impedances across the loads. Hence, the thicker or thinner regions of the leg can be preferentially heated by using a coupling medium with lower or higher salinity, respectively. Uniform power absorption along the mouse leg required that the coupling medium had equivalent electrical properties to those of tissue.