A head and neck hyperthermia applicator: theoretical antenna array design.
OBJECTIVE
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.


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 approximately 21% decrease in aPA. By changing the orientation of the patients with respect to the array an increase by approximately 11% was obtained. Increase of the amount of antenna rings led to a better focussing of the power (1 --> 2/3: approximately 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.
Paulides
Margarethus M
MM
Erasmus MC - Daniel den Hoed Cancer Centre, Department of Radiation Oncology, Section Hyperthermia, PO box 5201, NL-3008 AE Rotterdam, The Netherlands. M.Paulides@ErasmusMC.nI
Bakker
Jurriaan F
JF
Zwamborn
Adrianus P M
AP
Van Rhoon
Gerard C
GC
D006257:Head / Q000033:anatomy & histology* / Q000473:pathology; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods; D008962:Models, Theoretical; D009333:Neck / Q000033:anatomy & histology* / Q000473:pathology