title: Ultrasound-based elastography: a novel approach to assess radio frequency ablation of liver masses performed with expandable ablation probes: a feasibility study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the technical feasibility of ultrasound-based elastography as a tool for assessing the size and shape of the coagulation necrosis caused by radio frequency ablation (RFA) probes using expandable electrodes ex vivo as well as in a patient with a liver metastasis.
  
  
  METHODS
  A commercially available expandable RFA probe was used to create a 3-cm ablation in a piece of bovine liver. The ablation probe was used in situ to induce tissue deformation for elastography before and after ablation. Ultrasonic radio frequency data were processed to generate elasticity strain images. The appearance of the ablation zone was compared with magnetic resonance imaging and a gross section specimen. One patient with malignant metastatic disease to the liver and a clinical indication for RFA was investigated for the feasibility of percutaneous elastography of RFA using the same technique. Sonographic strain images were compared with the appearance of the nonenhancing ablation zone on contrast-enhanced computed tomography.
  
  
  RESULTS
  Ex vivo, the ablation zone on ultrasound-based elastography was represented by an area of increased stiffness and was well demarcated from the nonablated surrounding tissue. The size and shape of the ablated zone on the strain image correlated well with the gross specimen and the magnetic resonance imaging appearance. Strain images obtained from the patient showed results similar to those of the ex vivo experiment and correlated well with the nonenhancing area of ablation on contrast-enhanced computed tomography.
  
  
  CONCLUSIONS
  Ultrasound-based elastography may be a promising tool for displaying the ablation zone created by expandable RFA probes.
authors.affiliation: Department of Radiology, University of Washington Medical Center, Seattle, WA 98195-7115 USA. orpheus@u.washington.edu
authors.forename: Orpheus
authors.initials: O
authors.lastname: Kolokythas
authors.forename: Thomas
authors.initials: T
authors.lastname: Gauthier
authors.forename: Anna T
authors.initials: AT
authors.lastname: Fernandez
authors.forename: Hua
authors.initials: H
authors.lastname: Xie
authors.forename: Brian A
authors.initials: BA
authors.lastname: Timm
authors.forename: Carlos
authors.initials: C
authors.lastname: Cuevas
authors.forename: Manjiri K
authors.initials: MK
authors.lastname: Dighe
authors.forename: Lee M
authors.initials: LM
authors.lastname: Mitsumori
authors.forename: Matt F
authors.initials: MF
authors.lastname: Bruce
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Herzka
authors.forename: Gaurav K
authors.initials: GK
authors.lastname: Goswami
authors.forename: R Torrance
authors.initials: RT
authors.lastname: Andrews
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Oas
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Dubinsky
authors.forename: Bill H
authors.initials: BH
authors.lastname: Warren
mesh_terms: D000328:Adult; D000465:Algorithms; D000818:Animals; D017115:Catheter Ablation; D002417:Cattle; D003287:Contrast Media; D004548:Elasticity; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000601:surgery*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary / Q000601:surgery*; D009336:Necrosis; D018084:Ultrasonography, Interventional / Q000295:instrumentation*
chemical_list: D003287:Contrast Media