Dual Band Coaxial Y-Monopole for Hyperthermia Treatment of Cervical Cancer Delivered Through an Intrauterine Tandem

Abstract

In this work, we report a coaxial antenna consisting of a flexible Y-monopole with dual-band operation and low-profile wideband flexible ferrite choke for delivering localized HT treatment at shallow insertion depth of 50 mm inside the cervix using custom fabricated non-metallic intrauterine cervix tandem of 8 mm outer diameter and 1 mm wall thickness. Variable treatment coverage was achieved by selecting the excitation of the dual-band Y-monopole as 915 and 1300 MHz. The Y-monopole is a coaxial wire with a Y-split in the exposed inner conductor and wideband flexible ferrite sheet on the outer conductor to suppress the secondary current. The water loaded Y-monopole inside the intrauterine tandem cervix applicator with 15° bend angle resonated at 915 and 1300 MHz for arm lengths of 21 and 13.5 mm, respectively. The heating characteristics of Y-monopole was assessed using tissue-mimicking phantoms. Phantom measurements indicate dual band operation with power reflection coefficient $ \leq -$ 24 dB at 915 and 1300 MHz. The measured extents of 25% axial specific absorption rate in tissue phantom at 915 and 1300 MHz is 39.4 and 28.4 mm, respectively. Localized power deposition with $\Delta T = 3$ °C iso-contour of 46.3 mm × 39.2 mm and 37 mm × 31 mm along axial and radial directions was measured at 915 and 1300 MHz, respectively. Phantom measurements demonstrate the ability of the proposed antenna to deliver variable treatment volume to the cervix through 15° intrauterine tandem.