Development and evaluation of a three-dimensional hyperthermia applicator with Water-COated Antennas (WACOA).
A novel twelve-channel three-dimensional (3-D) hyperthermia applicator has been developed and evaluated, which consists of twelve separate WAter COated Antenna (WACOA) modules. The modules are arranged in three transversal antenna rings (sub-arrays) and are placed into an acrylic applicator frame as cartridge-like elements in a staggered arrangement. The operating frequency is 100 MHz. For the design of the applicator, the finite-difference time-domain (FDTD) method was used. The applicator's dimensions allow its placement into the gantry of a magnetic resonance (MR) tomograph. The WACOA modules are designed as MR-compatible specially shaped metallic cylindrical dipole structures that are placed into hermetically closed water-filled cassettes. Due to the design of the dipole structures, only a conventional coaxial feed circuitry is needed, and no external impedance matching networks are necessary. Instead, fine on-line impedance matching is realized using adjustable tuning rods and matching rings, both elements being parts of the radiating antenna structure. Experimental and numerical evaluations demonstrate a good stability of impedance matching, a low inter-channel coupling of less than -20 dB, and a good ability of field pattern steering.
Nadobny
Jacek
J
Center of Radiation Medicine, Campus Virchow-Klinikum, Charité Medical Center, Humboldt University at Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. jacek.nadobny@charite.de
Wlodarczyk
Waldemar
W
Westhoff
Lothar
L
Gellermann
Johanna
J
Rau
Beate
B
Mönich
Gerhard
G
Wust
Peter
P
D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D017097:Electric Impedance; D006979:Hyperthermia, Induced / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D014867:Water