Antenna Arrangement in UWB Helmet Brain Applicators for Deep Microwave Hyperthermia

Simple Summar: Despite the promising results of earlier studies on glioblastomas, hyperthermia is currently not applied in the treatment of brain cancer. Focused intracranial heating is a challenging task due to the presence of critical organs and their extra sensitivity to elevated temperatures. In this contribution, we introduce a new concept to design UWB applicators to achieve adequate temperatures in large brain tumors while protecting the healthy tissues from overheating. We introduce a fast E-field approximation scheme to quickly explore a large number of array configurations to determine the most optimal antenna arrangement around the head with respect to the multiple objectives and requirements of clinical hyperthermia. The proposed solution manages to achieve the level of tumor coverage and hot-spot suppression that is necessary for a successful treatment. The results show that the method is accurate enough to provide qualitative indications about the most suitable antenna arrangement for a given tumor shape and location, while yielding higher target temperatures than annular antenna arrays. Deep microwave hyperthermia applicators are typically designed as narrow-band conformal antenna arrays with equally spaced elements, arranged in one or more rings. This solution, while adequate for most body regions, might be sub-optimal for brain treatments. The introduction of ultra-wide-band semi-spherical applicators, with elements arranged around the head and not necessarily aligned, has the potential to enhance the selective thermal dose delivery in this challenging anatomical region. However, the additional degrees of freedom in this design make the problem non-trivial. We address this by treating the antenna arrangement as a global SAR-based optimization process aiming at maximizing target coverage and hot-spot suppression in a given patient. To enable the quick evaluation of a certain arrangement, we propose a novel E-field interpolation technique which calculates the field generated by an antenna at any location around the scalp from a limited number of initial simulations. We evaluate the approximation error against full array simulations. We demonstrate the design technique in the optimization of a helmet applicator for the treatment of a medulloblastoma in a paediatric patient. The optimized applicator achieves 0.3 ? higher T90 than a conventional ring applicator with the same number of elements.

Automated summary

Despite previous hopeful studies, hyperthermia is not currently used in the treatment of brain cancer. This study introduces a new concept of designing ultra-wideband applicators to achieve adequate temperatures in large brain tumors while protecting healthy tissues. A fast E-field approximation scheme is proposed to optimize antenna arrangements for clinical hyperthermia. The results show higher target temperatures and better tumor coverage compared to conventional antenna arrays.