The potential of constrained SAR focusing for hyperthermia treatment planning: analysis for the head & neck region

• Published in: Physics in medicine & biology Vol. 64; no. 1; p. 15013
• Main Authors: Bellizzi, G G, Drizdal, T, van Rhoon, G C, Crocco, L, Isernia, T, Paulides, M M
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 21.12.2018
• Subjects: constrained optimization; convex programming; SAR; treatment planning; Constrained Optimization; SAR; Convex Programming; Treatment Planning
• ISSN: 0031-9155; 1361-6560; 1361-6560
• DOI: 10.1088/1361-6560/aaf0c4

Clinical trials have shown that hyperthermia is a potent adjuvant to conventional cancer treatments, but the temperatures currently achieved in the clinic are still suboptimal. Hyperthermia treatment planning simulations have potential to improve the heating profile of phased-array applicators. An important open challenge is the development of an effective optimization procedure that enables uniform heating of the target region while keeping temperature below a threshold in healthy tissues. In this work, we analyzed the effectiveness and efficiency of a recently proposed optimization approach, i.e. focusing via constrained power optimization (FOCO), using 3D simulations of twelve clinical patient specific models. FOCO performance was compared against a clinically used particle swarm based optimization approach. Evaluation metrics were target coverage at the 25% iso-SAR level, target hotspot quotient, median target temperature (T50) and computational requirements. Our results show that, on average, constrained power focusing performs slightly better than the clinical benchmark (T50 °C), but outperforms this clinical benchmark for large target volumes (40 cm, T50 °C). In addition, the results are achieved in a shorter time (%) and are repeatable because the approach is formulated as a convex optimization problem.