In hyperthermia, the general opinion is that pre-treatment optimization of treatment settings requires a patient-specific model. For deep pelvic hyperthermia treatment planning (HTP), tissue models comprising four tissue categories are currently discriminated. For head and neck HTP, we found that more tissues are required for increasing accuracy. In this work, we evaluated the impact of the number of segmented tissues on the predicted specific absorption rate (SAR) for the pelvic region. Highly detailed anatomical models of five healthy volunteers were selected from a virtual database. For each model, seven lists with varying levels of segmentation detail were defined and used as an input for a modeling study. SAR changes were quantified using the change in target-to-hotspot-quotient and maximum SAR relative differences, with respect to the most detailed patient model. The main finding of this study was that the inclusion of high water content tissues in the segmentation may result in a clinically relevant impact on the SAR distribution and on the predicted hyperthermia treatment quality when considering our pre-established thresholds. In general, our results underline the current clinical segmentation protocol and help to prioritize any improvements.

Department of Biomedical Technology Czech Technical University Prague nam Sitna 3105 272 01 Kladno Czech Republic

Department of Radiation Oncology Erasmus MC Cancer Institute 3015 GD Rotterdam The Netherlands

Department of Radiation Oncology Erasmus MC Cancer Institute 3015 GD Rotterdam The Netherlands Department of Radiation Science and Technology Faculty of Applied Sciences Delft University of Technology 2629 JB Delft The Netherlands

Department of Radiation Oncology Erasmus MC Cancer Institute 3015 GD Rotterdam The Netherlands Electromagnetics for Care and Cure Department of Electrical Engineering Eindhoven University of Technology 5600 MB Eindhoven The Netherlands

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