Evaluation of a patch antenna applicator for time reversal hyperthemia

Purpose: 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. Materials and 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 mm2 (9 × 20 mm) (90% iso-SAR), was obtained by using 16 antennas at frequency 900 MHz. The largest focusing area of 280 mm2 (13 × 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 mm2 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.