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Insulated coaxial slot antennas (ICSA) and Insulated dipole
antennas (IDA) are widely used in interstitial
microwavehyperthermia. In this paper, wavenumber and
characteristicimpedance models of insulated dipole antenna (IDA)
in a single-layer catheter discussed by King et al. [12] are
extended to the cases of IDA and ICSA in a two-layer catheter.
Openings at both sides of the feed gap between arm one and arm
two of theuniform ICSA are used to obtain two access current
paths to shorten the physical length of the ICSA when compared
with IDA. Moreover, input impedance of the ICSA depends upon
the insertion depth, different insertion depths will lead to
different return loss (S11). In order to solve the impedance
matching problem, a quarter-wavelength choke is also imposed at
the feed of the ICSA to prevent the current from flowing
backward to the generator. Besides, an efficient and systematic
designoptimization method is proposed for the design of ICSA to
obtainthe desired current distribution along the axis of the
antenna and thespatial specific absorption rate (SAR) pattern
under good impedancematching. By the help of the efficient and
systematic designoptimization of ICSA, we are capable of
controlling the heating volume to fit into the specific shape
and size of each individual tumor, and to prevent from
corrupting the healthy tissues due to unnecessaryheating.
Moreover, an air cooling system [19] can also be applied inthe
two-layer catheter to take away the heat on the surface of the
antenna and gain more radiation efficiency for the antenna. Of
course, it will also reduce the pain of the patient and prevent
fromdamaging the antenna caused by the over heating temperature
on the antenna surface.
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