PARENT SESSION
1:30 PM to 3:30 PM
Monday, April 22, 2002
Poster Session 3 Heating Devices and High Temperature Therapy
Room: Nevada 1-2
(MP03-27) Experimental evaluation of compact low frequency dual-antenna applicators for hyperthermia of breast tumors.
Leybovich, Leonid*,1, Anil, Sethi1, Nesrin, Dogan1, 1 Department of Radiation Oncology, Maywood, Illinois
ABSTRACT-
As authors previously reported elsewhere, the experimental study of the dual-antenna design concept have shown that it was possible to design a compact low frequency EM applicator with improved depth of penetration and increased lateral heating effeciency. Based on this study, dual-antenna applicators of two aperture sizes (8x15 cm, for small to intermediate breasts, and 12x20 cm, for large breasts) were fabricated and experimentally tested using breast-shaped phantoms. The applicators presented a very short waveguide (the distance from the antenna plane to the aperture was 3 cm). This applicators employed two antennas. The distance between antennas was equal to a quarter-wavelength of EM radiation. The total height of the applicators was 11 cm. Applicators were filled with deionized water. The weight was 1.5 kg (small applicator) and 3 kg (large applicator). Applicators were powered by a dual-channel low frequency amplifier (BSD Co.). Each applicator was equipped with integral water bolus. The boluses were connected to a water circulating system that maintained desired bolus temperature. Experimental study demonstrated that applicators had two operating frequencies: 115 and 175 MHz (small applicator) and 90 and 140 MHz (large applicator). Coupling of the applicator to the curved surface of the breast phantom was quite good (reflected power was 1-2% of forward power). The lateral heating efficiency of each applicator was about 0.7 (20% higher than the theoretical limit for a TE mode applicator). The depth of 50% SAR (depth of penetration) was 3 cm (small applicator) and 3.7 cm (large applicator). Clinical evaluation of these applicators have demonstrated that coupling of the applicators to the treatment site was very stable. Adequate temperature distribution were achieved in treating breast tumors as well as chest wall recurrencies.
KEYWORDS: electomagnetic, low frequency, applicators, breast tumors