title: Which parameters are needed for targeting a multitined radiofrequency device--an approach to a simple algorithm.
abstract: BACKGROUND
  The use of radiofrequency ablation (RFA) for treatment of liver malignancies is limited by the high rate of local recurrences. The aim of this experimental study was to evaluate parameters describing the reproducible target volume of a RFA procedure in order to facilitate better applicator placement.
  
  
  METHODS
  RFA was performed in perfused and nonperfused pig livers. The following parameters were measured: axial and transverse diameter, front margin, coagulation center, diameter of sphere ablated (D(S)), distance to center (DC), and volume. Graphic overlays were utilized to visualize variability. Parameters were evaluated for Rita XL (2 algorithms), LeVeen, and Rita Xli applicators.
  
  
  RESULTS
  The best prediction of a reproducibly ablated target volume can be made by the diameter of the sphere ablated and the distance of the applicator tip to center of the sphere (DC). The spheres were significantly different in diameter (D(S)) depending on the applicator Rita XL 29 +/- 6 mm, Rita XL(wet) 35 +/- 5 mm, LeVeen 35 +/- 8 mm, Rita Xli 44 +/- 5 mm (perfused livers, p < 0.001). Graphic overlay demonstrated differences in variability that can influence the reliability of the system.
  
  
  CONCLUSIONS
  D(S) and DC as specific values for each applicator and algorithm facilitate a placement of the applicator relative to the target volume that maximizes the chance of complete ablation.
authors.affiliation: Department of Visceral and Vascular Surgery, University of Cologne, Joseph-Stelzmann-Strasse 9, 50931, Cologne, Germany. dirk.stippel@uni-koeln.de
authors.forename: Dirk L
authors.initials: DL
authors.lastname: Stippel
authors.forename: Christopher
authors.initials: C
authors.lastname: Bangard
authors.forename: Klaus
authors.initials: K
authors.lastname: Prenzel
authors.forename: Selim
authors.initials: S
authors.lastname: Yavuzyasar
authors.forename: Jürgen H
authors.initials: JH
authors.lastname: Fischer
authors.forename: Arnulf H
authors.initials: AH
authors.lastname: Hölscher
mesh_terms: D000465:Algorithms; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D017097:Electric Impedance; D008113:Liver Neoplasms / Q000473:pathology / Q000601:surgery*; D009336:Necrosis; D013552:Swine