title: A multi-step, incremental expansion method for radio frequency ablation: optimization of the procedure to prevent increases in intra-tumor pressure and to reduce the ablation time.
abstract: OBJECTIVE
  Radio frequency ablation (RFA) has been accepted clinically as a useful local treatment for hepatocellular carcinoma (HCC). However, intra-hepatic recurrence after RFA has been reported. We initially hypothesized that recurrence was attributable to increases in intra-tumor pressure during RFA, and we subsequently measured the pressure and optimized the procedure.
  
  
  METHODS
  A block of pig liver sealed in a rigid plastic case was used as a model of an HCC tumor with a capsule. We compared the pressure between a single-step full expansion of the needle (single-step method) and incremental, stepwise expansion (multi-step method), and evaluated the effect of varying the electrical power. Finally, we performed a preliminary comparison of the ablation times for these methods in HCC cases.
  
  
  RESULTS
  The multi-step method resulted in a significantly lower pressure and shorter total ablation time than the single-step method. Furthermore, incremental expansion in 10 steps resulted in a lower pressure and shorter ablation time than four steps. Seventy W-ablation resulted in a lower pressure and shorter time than 30- or 50 W-ablation. In HCC cases, the multiple-step method had a significantly shorter ablation time than the single-step method.
  
  
  CONCLUSIONS
  The multi-step method can be recommended to reduce the ablation time, and suppress the increase in pressure.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kotoh
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakamuta
authors.forename: Shusuke
authors.initials: S
authors.lastname: Morizono
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Kohjima
authors.forename: Eiichirou
authors.initials: E
authors.lastname: Arimura
authors.forename: Marie
authors.initials: M
authors.lastname: Fukushima
authors.forename: Munechika
authors.initials: M
authors.lastname: Enjoji
authors.forename: Hironori
authors.initials: H
authors.lastname: Sakai
authors.forename: Hajime
authors.initials: H
authors.lastname: Nawata
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D010865:Pilot Projects; D010969:Plastics; D011312:Pressure; D013552:Swine; D013997:Time Factors
chemical_list: D010969:Plastics