title: Experimental and numerical investigation of feed-point parameters in a 3-D hyperthermia applicator using different FDTD models of feed networks.
abstract: Experimental and numerical methods were used to determine the coupling of energy in a multichannel three-dimensional hyperthermia applicator (SIGMA-Eye), consisting of 12 short dipole antenna pairs with stubs for impedance matching. The relationship between the amplitudes and phases of the forward waves from the amplifiers, to the resulting amplitudes and phases at the antenna feed-points was determined in terms of interaction matrices. Three measuring methods were used: 1) a differential probe soldered directly at the antenna feed-points; 2) an E-field sensor placed near the feed-points; and 3) measurements were made at the outputs of the amplifier. The measured data were compared with finite-difference time-domain (FDTD) calculations made with three different models. The first model assumes that single antennas are fed independently. The second model simulates antenna pairs connected to the transmission lines. The measured data correlate best with the latter FDTD model, resulting in an improvement of more than 20% and 20 degrees (average difference in amplitudes and phases) when compared with the two simpler FDTD models.
authors.affiliation: Charité-Campus Virchow Klinikum. Klinik für Strahlenheilkunde, Augustenburger Platz 1, 13353 Berlin, Germany. jacek.nadobny@charite.de
authors.forename: Jacek
authors.initials: J
authors.lastname: Nadobny
authors.forename: Horst
authors.initials: H
authors.lastname: Fähling
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hagmann
authors.forename: Paul F
authors.initials: PF
authors.lastname: Turner
authors.forename: Waldemar
authors.initials: W
authors.lastname: Wlodarczyk
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Gellermann
authors.forename: Peter
authors.initials: P
authors.lastname: Deuflhard
authors.forename: Peter
authors.initials: P
authors.lastname: Wust
mesh_terms: D003198:Computer Simulation; D017097:Electric Impedance; D004574:Electromagnetic Fields; D004867:Equipment Design; D020342:Finite Element Analysis; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation* / Q000379:methods*; D008954:Models, Biological; D009369:Neoplasms / Q000628:therapy*; D000078702:Radiofrequency Therapy; D012680:Sensitivity and Specificity