Design and optimization of a multi-band spiral antenna for frequency-dependent hyperthermia heating in head and neck cancer treatment.

This research presents a compact multi-band spiral antenna designed for frequency-dependent hyperthermia therapy in head and neck cancers. The antenna is designed on a low-cost FR4 substrate with overall dimensions of 70 × 70 × 1.6 mm3 and is optimized to cover the 915 MHz, 1.8 GHz, and 2.45 GHz frequency bands. Its geometry enables stable tri-band resonance with excellent impedance matching, ensuring efficient energy transfer into biological tissues. The antenna's performance is evaluated through S-parameter analysis, specific absorption rate (SAR) distribution, penetration depth (PD), and effective field size (EFS) using homogeneous and heterogeneous phantoms, as well as the Katja voxel model with and without a tumor. The thermal simulations confirm that therapeutic temperatures of 41-45 °C are achieved with low input powers between 2.5-6 W. At 2.45 GHz, the antenna provides localized heating for superficial tumors (≤ 3 cm), at 1.8 GHz it is effective for intermediate tumor depths (3-3.6 cm), and at 915 MHz it achieves deeper penetration for tumors located beyond 3.6 cm. Experimental validation using head-simulating liquid and ex vivo chicken tissue demonstrates good agreement with simulation results, confirming reliable and efficient heating. The proposed applicator offers a practical and versatile solution, enabling personalized hyperthermia therapy across a wide range of tumor depths in head and neck cancer treatment.