title: Radiofrequency ablation lesions in a pig liver model.
abstract: BACKGROUND
  Radiofrequency (RF) ablation has been reported as a means of liver tumor destruction. This study evaluates the use of ultrasound monitoring of radiofrequency lesion creation and describes the morphology, histologic characteristics, and vascular effects of radiofrequency ablations in a pig liver model.
  
  
  METHODS
  Hemodynamic monitoring was established and laparotomies were performed in 50-kg pigs. Under ultrasound guidance, radiofrequency needle probes were placed in the liver at predetermined locations. Radiofrequency energy was applied over 15 min to generate lesions 3 cm in diameter. Eighty lesions were generated in 10 animals. At the completion of the experiment, the lesions were examined with ultrasound and then excised for CT, gross, and histologic examination.
  
  
  RESULTS
  There were no adverse systemic effects. Ultrasound imaging demonstrated the size, shape, and position of the lesions. Gross examination demonstrated a core of ablated tissue with a surrounding 1- to 2-mm hemorrhagic perimeter. Lesion volumes averaged 12.8 cc(3) (range 5-34 cc(3)). Final lesion shape and size were frequently altered by the cooling effect of local blood flow. Histologic stains demonstrated microvascular thrombosis and coagulative necrosis within the lesions. There appeared to be 100% cellular destruction within the lesion by cytochemical staining.
  
  
  CONCLUSIONS
  We demonstrated that RF ablation is capable of killing large volumes of normal liver tissue; however, local vasculature plays a significant a role in defining the ultimate size and shape of the lesion created. This may interfere with the utility of radiofrequency ablation as a modality for local tumor control.
authors.affiliation: Department of Minimally Invasive Surgery, Legacy Portland Hospitals, Oregon Health Sciences University, Portland, Oregon 97227, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Hansen
authors.forename: S
authors.initials: S
authors.lastname: Rogers
authors.forename: C L
authors.initials: CL
authors.lastname: Corless
authors.forename: L L
authors.initials: LL
authors.lastname: Swanstrom
authors.forename: A E
authors.initials: AE
authors.lastname: Siperstien
mesh_terms: D000818:Animals; D008102:Liver Circulation; D008114:Liver Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D000078702:Radiofrequency Therapy; D013552:Swine; D014463:Ultrasonography