A new interstitial antenna for microwave ablation

Abstract

Abstract:We propose an interstitial coaxial antenna that can insert without a catheter for microwave ablation therapy, operating at 2.45 GHz. The cap of the antenna is an arrowhead that bonds copper plate and ceramic plate to suppress heat conduction in the tip direction. The temperature distribution in the improved liver phantom is measured by using the infrared thermography device. As a result, it is clarified that we nearly get the spherical distribution of an assumed tumor in shape.

A new interstitial choke embedded antenna for microwave ablation

“…The tumor is a sphere of a diameter of 16 mm centered 30 mm from the breast surface. We searched for the sizes of the choke that the temperature distribution becomes closer to spherical when W ¼ 2 mm [3]. Fig.…”

“…Fig. 2 shows the temperature distribution of the central vertical cross section (zx plane) of the breast model inserted of the antenna, where (a) represents the proposed antenna with the choke (L ¼ 18 mm, l ¼ 3 mm), and (b) and (c) represent the conventional antenna without the choke of the new cap [3] and copper cap, respectively. Also, the dotted circle represents the tumor, the heating time t ¼ 110 s, the breast and tumor temperatures T b ¼ 37°C, the air temperature T a ¼ 24°C, and the convection coefficient between the breast and the air H ¼ 50 W/m 2 ·°C.…”

“…At 2.45 GHz, the reflection coefficient jS 11 j of the proposed antenna was −2.8 dB, while those of the conventional antennas of the new cap and copper cap were −4.7 dB and −5.7 dB, respectively. The reason for poor jS 11 j of the proposed antenna is designed for the liver tumor therapy [3]. The P ¼ 10 W is given as the net input power because there are differences in the reflection coefficients of three antennas.…”

“…We previously devised a new non-catheter type coaxial-slot antenna constructed by a needle of ceramic and conductor [3]. The usefulness of this antenna has proved experimentally by using the liver phantom.…”

“…) are the whole and the enlarged choke part, respectively. The spacer between the coaxial inner and outer conductors is Teflon (relative permittivity: 2.1), and the cap is the arrowhead of ceramic (relative permittivity: 9.8) plate and copper plate [3]. The choke having a length of L and an adjusting length of l is newly embedded in the coaxial outer conductor.…”