Focal field concentration in interstitial hyperthermia with an array of linear polarization radiators

Until now, the problem of interstitial hyperthermia was solved as a forward problem. When a circular array of radiators is concerned, symmetrical SAR curves were obtained for equal antenna currents; and some authors changed the phases of the antenna currents as an arithmatical sequence and observed some changes of the patterns. In this paper, the inverse problem is solved. With a proper election of the phases and amplitudes of antenna currents, focal field concentration at certaion target points are obtained. If these target points are chosen closely in a certain region, then this region gets higher SAR values when compared to the case of equal currents. It is found that for the operating frequency 2.45 GHz, higher increments in SAR can be obtained. This incerement can be 13.84 dB for a single target point; and 11.14 dB for two target points chosen 1.128 cm apart. Similar results with less increments are obtained for 915 MHz.