title: Percutaneous radiofrequency (RF) thermal ablation of rabbit tumors embedded in fat: a model for RF ablation of breast tumors.
abstract: OBJECTIVE
  To develop an experimental tumor model for RF ablation of breast tumors surrounded by fat and to investigate the minimally invasive treatment of such tumors by saline-enhanced RF ablation monitored by ultrasound (US).
  
  
  METHODS
  Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits and monitored by B-mode US at regular intervals of 2 to 3 days. Saline-enhanced RF ablation (25-mm tip length) was performed 16 days after tumor implantation (10-minute treatment time, 28 W, 15 mL/h infusion of 0.9% NaCl, which was increased to 30 mL/h in cases of an impedance increase). Thermal lesion growth was monitored by B-mode US. Treatment was considered complete if no relapse was detectable histopathologically after a follow-up period of up to 3 weeks.
  
  
  RESULTS
  All tumor implantations were successful, reaching sizes from 5 to 38 mm 16 days after implantation. Tumors >20 mm showed central necrosis on US. Smaller tumors without signs of necrosis required greater needle perfusion to maintain constant needle-to-tissue impedance. Local relapses occurred in 14 of 27 tumors (51.8%), all with tumors >20 mm. In 12 cases, they were already detected sonographically. In 2 cases, "islands" of vital tumor were detected only during histopathological assessment.
  
  
  CONCLUSIONS
  VX2 tumors are implantable into hypovascular adipose tissue with a high success rate and may be used as a model for RF ablation of breast tumors. B-mode US is not suitable for guiding RF ablation of tumors embedded in fat. The method appears to be more successful with smaller tumors.
authors.affiliation: Department Medizinische Radiologie, Institut für Diagnostische Radiologie, Universitätsspital Zürich, Switzerland. thomas_boehm@gmx.net
authors.forename: T
authors.initials: T
authors.lastname: Boehm
authors.forename: A
authors.initials: A
authors.lastname: Malich
authors.forename: J R
authors.initials: JR
authors.lastname: Reichenbach
authors.forename: M
authors.initials: M
authors.lastname: Fleck
authors.forename: W A
authors.initials: WA
authors.lastname: Kaiser
mesh_terms: D000273:Adipose Tissue; D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D004566:Electrodes; D019060:Minimally Invasive Surgical Procedures; D009336:Necrosis; D011817:Rabbits; D011846:Radio Waves; D012186:Retroperitoneal Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D012965:Sodium Chloride / Q000008:administration & dosage; D014407:Tumor Cells, Cultured; D014463:Ultrasonography
chemical_list: D012965:Sodium Chloride