The Impact of Scalp’s Temperature in the Predicted LMiPD in the Tumor During TTFields Treatment for Glioblastoma Multiforme

Abstract

AbstractTumor Treating Fields (TTFields) is a cancer treatment technique used for glioblastoma multiforme (GBM). It consists in the application of an electric field (EF) in two perpendicular directions alternately by placing transducer arrays on the patient’s scalp. In-vitro studies showed that the higher the electric field in the tumor, the better are the outcomes of the therapy. Therefore, these arrays are strategically placed in positions that can optimize the EF, based on the results of computational simulations. However, due to the required daily usage of this technique, at least 18 hours per day, the temperature of head tissues increases inevitably. To ensure patient’s safety, the temperature of the scalp is monitored and kept around 39.5 °C by changing the injected current, which consequently changes the EF in the tumor. In this work, we studied the impact that accounting for the temperature of the scalp might have in the choice of which layout should be used during TTFields planning. We used both a simplified and a realistic head model in our studies. We solved Laplace’s equation for the electric potential and Pennes’ equation for the temperature distribution using COMSOL Multiphysics. The electric field in the tumor was evaluated using the local minimum power density (LMiPD) both when the temperature of the scalp was considered in treatment planning and when it was not. We concluded that the values of the LMiPD significantly decrease when the temperature is considered. Furthermore, layouts in which two pairs of different arrays are very close to each other lead to the appearance of a common temperature hotspot, and consequently to the most significant variations in the predicted LMiPD values. In future, TTFields treatment planning studies, considering the temperature of the scalp might be beneficial to improve the predictions of treatment effectiveness.