Effective heating for tumors with thermally significant blood vessels during hyperthermia treatment

Significant cooling effect by blood vessels, particularly in treated tumor region, during hyperthermia treatment has been recognized by researchers. The present study investigated a heating strategy, using a preheating zone and adaptive optimization, to effectively reduce the cooling effect as thermally significant blood vessels flowed through treated region during hyperthermia treatment. The preheating zone is located in a vessel's entrance region adjacent to treated tumor and the heating strategy attempted to elevate blood temperature before blood flowing into the treated region. We numerically calculated blood and tissue temperatures using 3-D models and the goal of treatment was to reach a uniform therapeutic temperature in the tumor region using the proposed heating strategy. Results showed first, for large blood vessels, the heating strategy effectively elevated blood temperature at the entrance of treated tumor and reduced total tumor power deposition. Consequently, it helped to reach the ideal treated temperature on tumor more effectively, and avoided extreme power deposition due to the cooling effect of blood vessels entering the treated region. For small blood vessels, the preheating zone could further improve the treatment result. Secondly, heating flowing blood with adaptive optimization results in a unique phenomenon along blood flow paths. That is a strong convective nature of blood flow, which creates high thermal gradients in the treated region. Thus, it plays a different and significant role in adaptive optimization process as compared to thermal diffusion of solid tissues.

► Cooling effects by blood flow during hyperthermia treatments could be improved.
► The preheating strategy places zone on the blood vessel next to treated tumor region.
► Higher preheating zone temperature and longer preheating zone length are helpful.
► The preheating could prevent extreme required power deposition in the tumor region.
► We proposed the preheating strategy using a single blood vessel and vascular model.