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Bimodal electric tissue ablation (BETA) - in-vivo evaluation of the effect of applying direct current before and during radiofrequency ablation of porcine liver

Cockburn, J.; Maddern, G.; Wemyss-Holden, S.
Fonte: W B Saunders Co Ltd Publicador: W B Saunders Co Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
96.35%
AIM: To examine the effect of applying increasing amounts of direct current (DC) before and during alternating current radiofrequency ablation of porcine liver. MATERIALS AND METHODS: Using a Radiotherapeutics RF3000 generator, a 9 V AC/DC transformer and a 16 G plain aluminium tube as an electrode, a control group of 24 porcine hepatic radiofrequency ablation zones was compared with 24 zones created using a bimodal electric tissue ablation (BETA) technique in three pigs. All ablations were terminated when tissue impedance rose to greater than 999 Omega or radiofrequency energy input fell below 5 W on three successive measurements taken at 1 min intervals. BETA ablations were performed in two phases: an initial phase of variable duration DC followed by a second phase during which standard radiofrequency ablation was applied simultaneously with DC. During this second phase, radiofrequency power input was regulated by the feedback circuitry of the RF3000 generator according to changes in tissue impedance. The diameters (mm) of each ablation zone were measured by two observers in two planes perpendicular to the plane of needle insertion. The mean short axis diameter of each ablation zone was subjected to statistical analysis. RESULTS: With increased duration of prior application of DC...

The future of radiofrequency ablation is looking BETA : short and long term studies of bimodal electric tissue ablation (BETA) in a porcine model.

Dobbins, Christopher
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
126.47%
Introduction: Radiofrequency ablation (RFA) is a popular method of treating unresectable liver tumours by the use of a high frequency, alternating electrical current that heats and destroys tumour cells. The size of the ablation is limited by localised charring of adjacent tissue that prevents further conduction of the radiofrequency current. In the clinical setting, this results in increased rates of local recurrence in tumours that are greater than 3 cm in diameter as multiple, overlapping ablations need to be performed to treat the one tumour. To overcome this problem, a modified form of RFA called Bimodal Electric Tissue Ablation (BETA) has been created. BETA adds a direct electrical current to the alternating radiofrequency current, thus establishing its bimodal character. When direct currents are used in biological tissues, water is transferred from anode to cathode by a process called electro-osmosis. By attaching the cathode to the radiofrequency electrode, water is attracted to the area thus preventing tissue desiccation and charring. The BETA circuit has been constructed and tested using a porcine model. The aims of the studies are to confirm that larger ablations can be produced with the BETA system and that it is safe to use in an animal model. Three studies have been performed to test these aims in porcine liver. Methods: The first study was designed to compare sizes of the ablation produced between standard RFA and the BETA circuit. This was followed by a long-term study to assess associated changes to liver function and pathological changes within the liver as well as identifying any other treatment related morbidity. The third study assessed the difference in ablation size and safety aspects when the positive electrode of the direct current circuitry was moved from small surface area under the skin to a large surface area on the skin. Results: Ablations with significantly larger diameters are created with the BETA circuit using a multi-tine needle (49.55 mm versus 27.78 mm...

Bimodal electric tissue ablation-modified radiofrequency ablation with a Le Veen electrode in a pig model

Dobbins, C.; Wemyss-Holden, S.; Cockburn, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.04%
Radiofrequency ablation (RFA) is a method of treating non-resectable liver tumors by use of a high-frequency alternating electrical current. Concerns have been raised as the local recurrence rates following treatment have been reported to be as high as 47%. The size of the ablation is limited by charring of adjacent tissues. It is hypothesized that by hydrating the liver, we can reduce charring, thus producing larger ablations, and that this can be achieved by addition of a direct electrical current to the electrical circuit. Using a pig model, standard RFA control ablations were created in the left lobe of the liver. Ablations using the modified circuit were created in the right lobe. At the end of the procedure, the pig was killed by lethal injection and the liver harvested. From the explanted liver, the diameter of each ablation was measured and the modified ablations were compared with controls using restricted maximum likelihood variance analysis. From 4 pigs, 14 controls and 12 modified ablations were produced. The mean diameter of the controls was 27.78 mm (± SE 3.37 mm). The mean diameter of the modified ablation was 49.55 mm (± SE 3.46 mm), which was significantly larger than the controls (P < 0.001). This study has shown that by modification of the standard RFA circuit with the addition of a direct electrical current...

Bimodal electric tissue ablation: Positive electrode studies

Dobbins, C.; Brennan, C.; Wemyss-Holden, S.; Cockburn, J.; Maddern, G.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
126.43%
Background: Bimodal electric tissue ablation is a novel variation to standard radiofrequency ablation that produces significantly larger ablations by the addition of a direct electrical current. The negative electrode is attached to the radiofrequency current and the positive electrode is placed nearby. It has been identified that an electrolytic injury can occur at the positive electrode site. It is suggested that by increasing the surface area that is in contact with the positive electrode, the risk of tissue injury is reduced. This hypothesis was tested in a pig model. Methods: Thirty-six ablations were carried out in the livers of six pigs (six ablations per pig). Two were standard radiofrequency ablation controls and two were carried out with positive electrode attached to a scalpel blade. Two were carried out with positive electrode attached to a grounding pad. After 48 h, liver was harvested and the ablation sizes were compared. Skin biopsies were taken from the scalpel site and one from the pad site and examined histopathologically. Results: The scalpel blade ablations were significantly larger than controls and the grounding pad ablations (P < 0.001). The grounding pad ablation was significantly larger than controls. The scalpel blade skin site showed full-thickness tissue injury. The grounding pad site appeared microscopically normal. Conclusion: By increasing the surface area that connects to the positive electrode...

Bimodal electric tissue ablation-long term studies of morbidity and pathological change

Dobbins, C.; Brennan, C.; Wemyss-Holden, S.; Cockburn, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
86.19%
Christopher Dobbins, Catriona Brennan, Simon Wemyss-Holden, John Cockburn, and Guy Maddern

Bimodal electric tissue ablation (BETA) - Effect of reversing the polarity of the direct current on the size of ablation

Tiong, L.; Finnie, J.; Field, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
126.53%
BACKGROUND: Bimodal electric tissue ablation (BETA) is a new technique that uses the direct current in electrolysis to improve the efficacy of radio frequency (RF) ablation. It was hypothesized that attaching the cathode of the electrolytic circuit to the RF electrode will increase the tissue hydration, therefore delaying tissue desiccation during ablation. Consequently, the ablation process can continue for a longer period of time and produce larger ablations. This hypothesis was tested by reversing the polarity of the electrolytic circuit, which theoretically would cause tissue desiccation and therefore produce smaller ablations. This new setup is called reversed polarity bimodal electric ablation (RP-BEA). MATERIALS AND METHODS: Three types of ablations standard radiofrequency ablation (RFA), BETA, and RP-BEA) were tested in a pig liver model. In BETA and RP-BEA, 9 V of direct current were provided for 10 min, after which the rf generator were switched on and both electrical circuits allowed to run concurrently. In all three setups, ablations were continued until "roll-off." The size of ablation was measured and compared with each other. RESULTS: The duration of ablation was significantly shorted in RP-BEA compared with standard RFA and BETA (48 s verus 148 s and 84 s...

Bimodal electric tissue ablation (BETA) compared with the Cool-Tip RFA system

Tiong, L.; Field, J.; Maddern, G.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
96.31%
Background:  Bimodal electric tissue ablation (BETA) incorporates the process of electrolysis into radiofrequency ablation (RFA) to increase the size of tissue ablation. This study investigated whether BETA could increase the efficacy of the Cool-Tip RF system (Covidien, Boulder, CO, USA) to produce larger ablations. It also investigated whether applying electrolysis only during the pretreatment phase (called electrochemical treatment (ECT)/RFA group) is as effective as BETA (where electrolysis was used during both the pretreatment and RFA phases). Methods:  A Cool-Tip RF system (Covidien) was used to test three types of ablations (RFA, BETA, and ECT/RFA) in a pig liver model. In BETA, 9 V of direct current was provided for 10 min, after which the RF generator was started and both electrical circuits were allowed to run concurrently. In ECT/RFA, however, the direct current circuit was switched off after 10 min of pretreatment and only RFA was performed as described above. Ablation sizes were measured in three dimensions. Results:  The size of ablations (transverse diameter A and B) produced by BETA and ECT/RFA was significantly larger compared with standard RFA (P < 0/001). BETA also created larger ablations compared with ECT/RFA (P < 0.001). Conclusion:  BETA could improve the efficacy of the Cool-Tip RF system (Covidien) to achieve larger ablations. The increased tissue hydration improved delivery of electrical energy to the tissues and delayed the process of desiccation...

Improving the safety and efficacy of bimodal electric tissue ablation.

Tiong, Leong Ung
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
96.44%
Introduction: Bimodal electric tissue ablation (BETA) is a new method of ablation, which combines the process of electrolysis with radiofrequency ablation (RFA) to increase the size of tissue ablations. The cathode of the electrolytic circuit is connected to the radiofrequency (RF) electrode to increase the surrounding tissue hydration. This allows the RFA process to continue for a longer period of time and therefore produce larger ablations. Previous research has shown that BETA could produce larger ablations compared to standard RFA and that it did not produce any significant short or long-term complications. The studies described here aim to increase the knowledge on how BETA works to facilitate its translation into clinical practice to treat liver tumours. Materials & Methods The first study tested whether BETA really acts by increasing the hydration of tissues around the RF electrode. This was achieved by reversing the polarity of the electrolytic circuit, which theoretically would produce smaller ablations compared to standard RFA. The second study assessed where would be the best location (skin, parietal peritoneum or liver) for the anode of the electrolytic circuit during a BETA process. The third experiment determined whether the principle of BETA could be incorporated into the Cool-Tip RF system...

Bimodal Electric Tissue Ablation (BETA): A study on ablation size when the anode is placed on the peritoneum and the liver

Tiong, L.; Finnie, J.; Field, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
126.44%
BACKGROUND: In bimodal electric tissue ablation (BETA), the cathode of the DC circuit is attached to the radiofrequency (RF) electrode to increase the surrounding tissue hydration. This will delay tissue desiccation and allowing the ablation process to continue for a longer period of time before "roll-off" occurs, resulting in larger ablations compared with standard radiofrequency ablation (RFA). Previous research showed that attaching the anode to the skin using electrosurgical grounding pads would reduce the efficacy of BETA because of the high electrical resistivity of the skin. This study investigated the ablation size produced when the anode was attached to the peritoneum (BETA-peritoneum) and the liver (BETA-liver) respectively. MATERIALS AND METHODS: The anode of the DC circuit in BETA was attached to the peritoneum and the liver in a pig model using ECG dots. In BETA, 9 V of DC was provided for 10 min, after which the radiofrequency generator were switched on and both electrical circuits allowed to run concurrently until "roll-off." The size of ablations produced was compared to when the anode attached to the skin (BETA-skin) and standard RFA, respectively. The sites of anode placement were examined for local tissue injury. RESULTS: The transverse diameters in BETA-peritoneum and BETA-liver were significantly larger compared with BETA-skin and standard RFA...

Experimental application of electrolysis in the treatment of liver and pancreatic tumours: Principles, preclinical and clinical observations and future perspectives

Gravante, G.; Ong, S.; Metcalfe, M.; Maddern, G.; Lloyd, D.; Dennison, A.
Fonte: Elsevier Sci Ltd Publicador: Elsevier Sci Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
56.06%
BACKGROUND: Electrolytic ablation (EA) is a treatment that destroys tissues through electrochemical changes in the local microenvironment. This review examined studies using EA for the treatment of liver and pancreatic tumours, in order to define the characteristics that could endow the technique with specific advantages compared with other ablative modalities. METHODS: Literature search of all studies focusing on liver and pancreas EA. RESULTS: A specific advantage of EA is its safety even when conducted close to major vessels, while a disadvantage is the longer ablation times compared to more frequently employed techniques. Bimodal electric tissue ablation modality combines radiofrequency with EA and produced significant larger ablation zones compared to EA or radiofrequency alone, reducing the time required for ablation. Pancreatic EA has been investigated in experimental studies that confirmed similar advantages to those found with liver ablation, but has never been evaluated on patients. Furthermore, few clinical studies examined the results of liver EA in the short-term but there is no appropriate follow-up to confirm any survival advantage. CONCLUSIONS: EA is a safe technique with the potential to treat lesions close to major vessels. Specific clinical studies are required to confirm the technique's safety and eventually demonstrate a survival advantage.; G. Gravante...