On heating head and neck tumours using the novel clinical em applicator: the HYPERcollar

Abstract Purpose: Definition of all features and the potential of the novel HYPERcollar applicator system for hyperthermia treatments in the head and neck (H&N) region. Methods and Materials: The HYPERcollar applicator consists of 1) an antenna ring, 2) a waterbolus system and 3) a positioning system. The specific absorption rate (SAR) profile of this applicator is investigated by performing infra-red (IR) measurements in a cylindrical phantom. Mandatory patient-specific treatment planning is performed as an object lesson to a patient with a laryngeal tumour and an artificial lymph node metastasis. Results: The comfort tests with healthy volunteers have revealed that the applicator provides su±cient comfort to maintain in treatment position for an hour: in our center the standard hyperthermia treatment duration. We further established that a central focus in the neck can be obtained, with 50% iso-SAR lengths of 3.5cm in transversal directions and 9-11cm in the axial direction (z). Using treatment planning by detailed electromagnetic simulations, we showed that the SAR pattern can be optimized to enable simultaneous encompassing a primary laryngeal tumour and a lymph node metastasis at the 25% iso-SAR level. Conclusions: A site-specific H&N applicator was designed that enables good control and sufficient possibilities for optimizing the SAR pattern. In an ongoing clinical feasibility study we will investigate the possibilities of heating various target regions in the neck with this apparatus.