Evaluation of a patch antenna applicator for time reversal hyperthemia.
OBJECTIVE
To describe the design, analysis and evaluation of a new antenna array system for microwave hyperthermia. The proposed antenna array was evaluated by the focusing method based on the time-reversal principle.


METHODS
Power absorption distributions in a cylindrical homogeneous and inhomogeneous phantom were calculated for the frequency range 500-900 MHz. Two set-ups with 12 and 16 antennas were analysed by comparing the changes in focusing areas enclosed by the 50%, 75% and 90% iso-SAR contours. For a more quantitative evaluation of the results the average power absorption ratio and remaining tissue maximum index were calculated.


RESULTS
The sharpest focusing area in the centre of the phantom, 151 mm(2) (9 x 20 mm) (90% iso-SAR), was obtained by using 16 antennas at frequency 900 MHz. The largest focusing area of 280 mm(2) (13 x 24 mm) (90% iso-SAR) was obtained by using 16 antennas at 500 MHz. The SAR focus was steered in the desired radial direction obtaining a 43 mm(2) 90% iso-SAR focus-width in a semi-three-dimensional neck phantom. The results showed qualitative agreement between three dimensions (3D) and two dimensions (2D) for the performance indicators.


CONCLUSIONS
The conducted study confirms the feasibility of the time-reversal-based focusing methods for microwave hyperthermia. The proposed system shows promise and is suitable for further development in the treatment of head and neck tumours, and extremities application.
Dobsícek Trefná
Hana
H
Department of Signals and Systems, Chalmers University of Technology, Gothenburg, Sweden. hanatre@chalmers.se
Vrba
Jan
J
Persson
Mikael
M
D004867:Equipment Design; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods; D008872:Microwaves; D019047:Phantoms, Imaging