2.3.2. Objective Functions

The aim in clinical hyperthermia is always to maximize the tumor temperature, and T90, i.e., the temperature at least achieved in 90% of the tumor volume is an important clinical parameter. Therefore, the objective functions used maximized T90. Hard constraints were applied to avoid a large temperature increase at other potential hot spot locations; to further minimize this temperature increase, also the use of additional penalty terms was evaluated. Penalty terms were defined for either the maximum increase in all potential hot spot temperatures, or the sum of the increase in potential hot spot temperatures. This yields the following three optimization goals:

all subject to hard normal tissue and antenna constraints, as described in Section 2.3.1. T_old and T_new represent the hot spot temperature before and after the re-optimization, respectively.