A head and neck hyperthermia applicator: theoretical antenna array design

Purpose: Investigation into the feasibility of a circular array of dipole antennas to deposit RF-energy centrally in the neck as a function of: (1) patient positioning, (2) antenna ring radius, (3) number of antenna rings, (4) number of antennas per ring and (5) distance between antenna rings. Materials and Methods: Power absorption (PA) distributions in realistic, head and neck, anatomy models are calculated at 433 MHz. Relative PA distributions corresponding to different set-ups were analysed using the ratio of the average PA (aPA) in the target and neck region. Results: Enlarging the antenna ring radius from 12.5 cm to 25 cm resulted in a ~21% decrease in aPA. By changing the orientation of the patients with respect to the array an increase by ~11% was obtained. Increase of the amount of antenna rings led to a better focussing of the power (1 ¿ 2/3: ~17%). Increase of the distance between the antenna rings resulted in a smaller (more target region conformal) focus but also a decreased power penetration. Conclusions: A single optimum array setup suitable for all patients is difficult to define. Based on the results and practical limitations a setup consisting of two rings of six antennas with a radius of 20 cm and 6 cm array spacing is considered a good choice providing the ability to heat the majority of patients.