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Author: search.filters.author.Lertprasert, P.Subject: search.filters.subject.Microwave ablation

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    Microwave ablation system design to study the effects of coaxial antenna on in-vitro animal tissue
    (2014-01-01)
    Chaichanyut, M.
    ;
    Lertprasert, P.
    ;
    Tungjitkusolmun, S.
    This paper presents a novel low cost microwave ablation system design to study the effects of coaxial antenna on In Vitro animal tissues. The system utilizes a high-voltage power supply so that the magnetron can generate a microwave field continuously, and its output power can be adjusted from 10 - 80 W at frequency of 2.45GHz. We control output microwave power level by using control the magnetron power supply, which it is an important part of a microwave heating system. Power control of the magnetron’s power supply is desired for microwave heating to enhance performance and to provide system flexibility. The high frequency switching technique in the power supply control is costly and complicated. In another way, pulsing the output power of the magnetron can be simply realized with TRIAC, but in that case the magnetron does not operate continuously. The proposed circuit is a simple one with TRIAC. The power control is achieved by controlling the triggering events at appropriate phase angle of the household 220V. Experimental protocol was composed by a radiation system and a thermometry system. Coaxial antenna works at 2.45 GHz, power apply during experiments was 10W×8min; 20W×4min; 40W×2min and 80W×1min. Thermal sensors were placed next to the antenna at 1mm., a large number of experiments on porcine liver are carried out, the temperature distribution within the liver are measured and illustrated, for cases of different injected microwave power and ablation time. In addition, the ablation areas in cases of different input microwave powers are measured also. All these results indicate the potential validity of this system on medical treatment of liver cancer of human body.
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    The modeling techniques for analyses of electromagnetic distributions and reflection coefficients for microwave ablation
    (2014-01-01)
    Chaichanyut, M.
    ;
    Lertprasert, P.
    ;
    Tungjitkusolmun, S.
    many advantages of microwave ablation over the other ablative therapies in the field of liver tumor ablation have driven researchers to develop innovative interstitial microwave antennas to effectively treat deep seated, nonresectable hepatic tumors. A new coaxial antenna for microwave ablation therapies has been proposed in this research paper. Three dimensional Finite Element Method (FEM) has been used to design the results of the proposed antenna. Objective metrics for assessing the characteristics of helix antennas for microwave ablation by analyzing the electromagnetic field distributions and reflection coefficients for efficiency of antenna has been specified and verified for the proposed antenna, at frequency of 2.45GHz. Our simulation results, Relative permittivity at 2.45 GHz during thermal ablation. Accumulated ablation times noted on each figure to identify temporal variations. Values tended to drop quickly in all cases when temperatures reached 100 °C and continued to drop as temperature was maintained and the tissue became more dehydrated. Changes were irreversible as tissue returned to baseline temperatures. We designs the antenna matching obtained at 2.45 GHz. During thermal ablation, the reflection coefficients it can be noted that the antenna resonance shifts toward higher frequencies and the electric field distribution at the near field region changing follow the temperature variations in tumor tissue.
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    Comparison temperature distribution between microwave and radio-frequency ablation probe in hepatic cancer
    (2007-01-01)
    Chaichanyut, M.
    ;
    Tungjitkusolmun, S.
    ;
    Potejanasaja, I.
    ;
    Lertprasert, P.
    This paper presents three-dimensional finite element analyses of hepatic cancer ablation. The analyses performed in this paper are composed of two systems. In the first system, the simulation was microwave ablation by using open-tip monopole antenna. We analyses microwave ablation at frequency of 2.45GHz. Additional simulations of radiofrequency ablation by using monopolar probe. All simulations, we studied and compared the characteristics of the electric field and temperature distributions between monopole antenna and monopolar probe. From the simulation results, the electric field distribution of open-tip monopole was a wide electric field distribution while the electric field distribution of monopolar has a narrower. The temperature distribution has distributed same with electric field distribution. The temperature distribution of open-tip monopole was larger when compared with monopolar probe.
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    Length effect of metal-tip monopole antenna to temperature distributions for microwave ablation
    (2007-01-01)
    Chaichanyut, M.
    ;
    Lertprasert, P.
    ;
    Phonphruksa, P.
    ;
    Tungjitkusolmun, S.
    This paper present three-dimensional finite element analyses of hepatic cancer. We studied the characteristics of metal-tip monopole (MTM) antennas for microwave ablation by analyzing the length effect of metal at the antenna tip. We analyses microwave ablation at frequency of 2.45GHz.The length of metallic tip (ht) are varied so as to observe the effect on the temperature distribution. Simulations the length of metallic tip are 1mm, 2mm and 4 mm. From the simulation results, we considered the hepatic cancer region where temperature exceeds 50 °C. The lengths of metallic tip are 1 mm, 2 mm and 4mm had similar temperature distribution profiles and the maximum temperature occurred around the tips of the antennas. In case the length of metallic tip is 4mm, the temperature distribution was widest and induced the highest temperature in cancer tissue. In addition, the temperature distribution was narrowly shaped along the length in regions the shaft body of the antenna. For case the length of metallic tip is 2 mm, the temperature had minimum in cancer tissue and can be minimum ablation cancer tissue (17.34cm<sup>3</sup>). For case the length of metallic tip is 1 mm, this case can be maximum ablation cancer tissue (18.67cm<sup>3</sup>).