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Access type: UnknownSubject: search.filters.subject.Radio-frequency ablation

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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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    Finite-element analysis of hepatic multiple probe radio-frequency ablation
    (2002-07-30)
    Haemmerich, Dieter
    ;
    Tungjitkusolmun, Supan
    ;
    Staelin, S. Tyler
    ;
    Lee, Fred T.
    ;
    Mahvi, David M.
    Radio-frequency (RF) ablation is an important means of treatment of nonresectable primary and metastatic liver tumors. RF ablation, unlike cryoablation (a method of tumor destruction that utilizes cold rather than heat), must be performed with a single probe placed serially. The ablation of any but the smallest tumor requires the use of multiple overlapping treatment zones. We evaluated the performance of a configuration incorporating two hooked probes (RITA model 30). The probes were lined up along the same axis in parallel 20 mm apart. Three different modes applied voltage to the probes. The first mode applied energy in monopolar mode (current flows from both probes to a dispersive electrode). The second mode applied the energy to the probes in bipolar mode (current flows from one probe to the other). The third method applied the energy sequentially in monopolar mode (in 2-s intervals switched between the probes). We used the finite-element method (FEM) and analyzed the electric potential profile and the temperature distribution at the end of simulation of a 12-min ablation. The alternating monopolar mode allowed precise independent control of the amount of energy deposited at each probe. The bipolar mode created the highest temperature in the area between the probes in the configuration we examined. The monopolar mode showed the worst performance since the two probes in close vicinity create a disadvantageous electric field configuration. We, thus, conclude that alternating monopolar RF ablation is superior to the other two methods.
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    Three-dimensional finite-element analyses for radio-frequency hepatic tumor ablation
    (2002-01-05)
    Tungjitkusolmun, Supan
    ;
    Staelin, S. Tyler
    ;
    Haemmerich, Dieter
    ;
    Tsai, Jang Zern
    ;
    Cao, Hong
    Radio-frequency (RF) hepatic ablation, offers an alternative method for the treatment of hepatic malignancies. We employed finite-element method (FEM) analysis to determine tissue temperature distribution during RF hepatic ablation. We constructed three-dimensional (3-D) thermal-electrical FEM models consisting of a four-tine RF probe, hepatic tissue, and a large blood vessel (10-mm diameter) located at different locations. We simulated our FEM analyses under temperature-controlled (90 °C) 8-min ablation. We also present a preliminary result from a simplified two-dimensional (2-D) FEM model that includes a bifurcated blood vessel. Lesion shapes created by the four-tine RF probe were mushroom-like, and were limited by the blood vessel. When the distance of the blood vessel was 5 mm from the nearest distal electrode 1) in the 3-D model, the maximum tissue temperature (hot spot) appeared next to electrods A. The location of the hot spot was adjacent to another electrode 2) on the opposite side when the blood vessel was 1 mm from electrode A. The temperature distribution in the 2-D model was highly nonuniform due to the presence of the bifurcated blood vessel. Underdosed areas might be present next to the blood vessel from which the tumor can regenerate.
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    Guidelines for predicting lesion size at common endocardial locations during radio-frequency ablation
    (2001-01-01)
    Tungjitkusolmun, Supan
    ;
    Vorperian, Vicken R.
    ;
    Bhavaraju, Naresh
    ;
    Cao, Hong
    ;
    Tsai, Jang Zern
    We used the finite element method to study the effect of radio-frequency (RF) catheter ablation on tissue heating and lesion formation at different intracardiac sites exposed to different regional blood velocities. We examined the effect of application of RF current in temperature- and power-controlled mode above and beneath the mitral valve annulus where the regional blood velocities are high and low respectively. We found that for temperature -controlled ablation, more power was delivered to maintain the preset tip temperature at sites of high local blood velocity than at sites of low local blood velocity. This induced more tissue heating and larger lesion volumes than ablations at low velocity regions. In contrast, for power-controlled ablation, tissue heating was less at sites of high compared with low local blood velocity for the same RF power setting. This resulted in smaller lesion volumes at sites of low local velocity. Our numerical analyzes showed that during temperature-controlled ablation at 60 °C, the lesion volumes at sites above and underneath the mitral valve were comparable when the duration of RF current application was 10 s. When the duration of RF application was extended to 60 s and 120 s, lesion volumes were 33.3% and 49.4% larger above the mitral valve than underneath the mitral valve. Also, with temperature-controlled ablation, tip temperature settings of 70 °C or greater were associated with a risk of tissue overheating during long ablations at high local blood velocity sites. In power-controlled ablation (20 W), the lesion volume formed underneath the mitral valve was 165.7% larger than the lesion volume above the mitral valve after 10 s of ablation. We summarized the guidelines for energy application at low and high flow regions.