title: Numerical analysis of the relationship between the area of target tissue necrosis and the size of target tissue in liver tumours with pulsed radiofrequency ablation.
abstract: OBJECTIVE
  Radiofrequency ablation (RFA) is currently restricted to the treatment of target tissues with a small size (<3 cm in diameter). To overcome this problem with RFA, some phenomena need to be understood first. The study presented in this paper investigated the relationship between the area of target tissue necrosis (TTN) and the size of target tissue in pulsed radiofrequency ablation (PRFA).
  
  
  METHODS
  Liver tumour, one of the common targets of RFA in clinical practice, was used as the target tissue in this study. Two types of pulsed RF power supply methods (half-square and half-sine) and three target tissues with different sizes (25 mm, 30 mm and 35 mm in diameter) were studied using finite element modelling. The finite element model (FEM) was validated by using an in vitro experiment with porcine liver tissue. The first roll-off occurrence or 720 s, whichever occurs first, was chosen as the ablation termination criterion in this study.
  
  
  RESULTS
  For each target tissue size, the largest TTN area was obtained using the maximum voltage applied (MVA) without roll-off occurrence. In this study, target tissues with a 25 mm diameter can be ablated cleanly but target tissues with 30-mm and 35-mm failed to be ablated.
  
  
  CONCLUSIONS
  The half-square PRFA could achieve a larger TTN area than the half-sine PRFA. The MVA decreases with an increase in the target tissue diameter in both the half-square PRFA and the half-sine PRFA. The findings of this study are in agreement with the clinical results that lesions (≥ 3 cm in diameter) have less favourable results from RFA.
authors.affiliation: a Division of Biomedical Engineering , University of Saskatchewan , Saskatoon , Canada .
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.affiliation: b Department of Surgery , University of Saskatchewan , Saskatoon , Canada .
authors.forename: Michael A J
authors.initials: MA
authors.lastname: Moser
authors.affiliation: c Department of Radiology and Diagnostic Imaging , University of Alberta , Edmonton , Canada .
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Zhang
authors.affiliation: b Department of Surgery , University of Saskatchewan , Saskatoon , Canada .
authors.forename: Yigang
authors.initials: Y
authors.lastname: Luo
authors.affiliation: a Division of Biomedical Engineering , University of Saskatchewan , Saskatoon , Canada .|d Complex and Intelligent Systems Centre, School of Mechanical and Power Engineering, East China University of Science and Technology , Shanghai , China , and.|e Department of Mechanical Engineering , University of Saskatchewan , Saskatoon , Saskatchewan , Canada .
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zhang
mesh_terms: D020342:Finite Element Analysis; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009336:Necrosis; D061208:Pulsed Radiofrequency Treatment
keywords: Finite element modelling; liver tumour; pulsed radiofrequency ablation; roll-off; target tissue necrosis