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Author: search.filters.author.Tungjitkusolmun, SupanSubject: search.filters.subject.RF ablation

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    Mechanical compliance of the endocardium
    (2002-12-01)
    Bin Choy, Young
    ;
    Cao, Hong
    ;
    Tungjitkusolmun, Supan
    ;
    Tsai, Jang Zern
    ;
    Haemmerich, Dieter
    Radio-frequency (RF) ablation is an accepted treatment for cardiac arrhythmias related to abnormal focal cardiac substrate. The penetration depth of the electrode into the endocardium affects lesion size, a critical determinant of success of RF ablation. We measured the relation between the mechanical compliance and the penetration depth of RF ablation catheter electrode at frequently ablated areas of the endocardium and examined the influence of time after death on mechanical properties of the tissue. We measured force versus time for eight insertion depths of the catheter electrode into full-thickness endocardial samples derived from the mitral valve annulus, the left ventricular free wall and the tricuspid valve annulus. We varied the time after death at 15, 40min, 3, 8, and 18h and repeated our measurements. At 15min after death, the first 0.5mm penetration depth caused the fastest relaxation at 55s. Force decay decreased dramatically at 15min after death as the penetration depth increased from 0.5 to 4mm. We used the force data sampled at 60s after insertion to approximate the elasticity. We observed the relations between the force versus the insertion depth. The force increased by a factor of 5 for the mitral valve annulus and 8 for the left free wall from 15min to 18h. We derived coefficients of a second-order polynomial equation relating the force data to insertion depth with R<sup>2</sup>>0.99. © 2002 Elsevier Science Ltd. All rights reserved.
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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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    Hepatic bipolar radio-frequency ablation between separated multiprong electrodes
    (2001-10-01)
    Haemmerich, Dieter
    ;
    Staelin, S. Tyler
    ;
    Tungjitkusolmun, Supan
    ;
    Lee, Fred T.
    ;
    Mahvi, David M.
    Radio-frequency (RF) ablation has become an important means of treatment of nonresectable primary and metastatic liver tumors. Major limitations are small lesion size, which make multiple applications necessary, and incomplete killing of tumor cells, resulting in high recurrence rates. We examined a new bipolar RF ablation method incorporating two probes with hooked electrodes (RITA model 30). We performed monopolar and bipolar in vivo experiments on three pigs. The electrodes were 2.5 cm apart and rotated 45° relative to each other. We used temperature-controlled mode at 95 °C. Lesion volumes were 3.9 ± 1.8 cm <sup>3</sup> (n = 7) for the monopolar case and 12.2 ± 3 cm <sup>3</sup> (n = 10) for the bipolar case. We generated finite-element models (FEMs) of monopolar and bipolar configurations. We analyzed the distribution of temperature and electric field of the finite element model. The lesion volumes for the FEM are 7.95 cm <sup>3</sup> for the monopolar and 18.79 cm <sup>3</sup> for the bipolar case. The new bipolar method creates larger lesions and is less dependent on local inhomogenities in liver tissue-such as blood perfusion-compared with monopolar RF ablation. A limitation of the new method is that the power dissipation of the two probes cannot be controlled independently in response to different conditions in the vicinity of each probe. This may result in nonuniform lesions and decreased lesion size.