Significance of blood vessels in optimization of absorbed power and temperature distributions during hyperthermia

This study investigated the significance of blood vessels in the absorbed power and temperature distributions when optimization was employed during hyperthermia. The treated tumor region was simulated using a three-dimensional (3D) tissue model embedded with a countercurrent blood vessel network (Huang et al., 1996). 3D temperature distributions are obtained by solving the conduction equation in the tissues and the convective energy equation with specified Nusselt number in the vessels. 3D absorbed power depositions are obtained by using optimization to reach a uniform temperature of 43 °C for the desired treated region. Results show that the absorbed power deposition for optimization with fine spatial resolution produces a uniform temperature distribution maintained at 43 °C in the desired treated tumor region except for some cold spots and/or small cold strips caused by thermally significant large vessels. The amount of total absorbed power suggests that a region with thermally significant vasculature requires much more power deposited than one without vasculature. In addition, optimization with coarse spatial resolution results in a highly inhomogeneous temperature distribution in the treated region due to the strong cooling effect of blood vessels. Therefore, prior to hyperthermia treatments, thermally significant blood vessels should be identified and handled carefully to effectively reduce their strong cooling effect, particularly those vessels flowing into the treated region.