SAR distributions for 915 MHz interstitial microwave antennas used in hyperthermia for cancer therapy

Theoretical and experimental specific absorption rate (SAR) distributions are presented for single insulated antennas operating at 915 MHz in muscle phantom; the SAR is deduced from measured temperature rise. Results show that dipoles with lengths much shorter than their resonant length have a characteristically large reactive input impedance component and a substantially smaller absolute SAR magnitude than resonant dipoles. All cases investigated demonstrate that the maximum SAR occurs near the junction, regardless of insertion depth. Experimental results show that an antenna with the tip section equal to a quarter-wavelength and the insertion depth equal to a half-wavelength achieves a substantial increase in the longitudinal power distribution compared to other antenna designs that were evaluated.