title: Comparison of tissue pressure and ablation time between the LeVeen and cool-tip needle methods.
abstract: BACKGROUND
  Radio frequency ablation (RFA) has been accepted clinically as a useful local treatment for hepatocellular carcinoma (HCC). However, intrahepatic recurrence after RFA has been reported which might be attributable to increase in intra-tumor pressure during RFA. To reduce the pressure and ablation time, we developed a novel method of RFA, a multi-step method in which a LeVeen needle, an expansion-type electrode, is incrementally and stepwise expanded. We compared the maximal pressure during ablation and the total ablation time among the multi-step method, single-step method (a standard single-step full expansion with a LeVeen needle), and the method with a cool-tip electrode. Finally, we performed a preliminary comparison of the ablation times for these methods in HCC cases.
  
  
  RESULTS
  A block of pig liver sealed in a rigid plastic case was used as a model of an HCC tumor with a capsule. The multi-step method with the LeVeen electrode resulted in the lowest pressure as compared with the single-step or cool-tip methods. There was no significant difference in the ablation time between the multi-step and cool-tip ablation methods, although the single-step methods had longer ablation times than the other ablation procedures. In HCC cases, the multi-step method had a significantly shorter ablation time than the single-step or cool-tip methods.
  
  
  CONCLUSIONS
  We demonstrated that the multi-step method was useful to reduce the ablation time and to suppress the increase in pressure. The multi-step method using a LeVeen needle may be a clinically applicable procedure for RFA.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Japan. nakamuta@intmed3.med.kyushu-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakamuta
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Kohjima
authors.forename: Shusuke
authors.initials: S
authors.lastname: Morizono
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yoshimoto
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Miyagi
authors.forename: Hironori
authors.initials: H
authors.lastname: Sakai
authors.forename: Munechika
authors.initials: M
authors.lastname: Enjoji
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kotoh