title: Evaluation of a bipolar-cooled radiofrequency device for ablation of bone metastases: preclinical assessment in porcine vertebrae.
abstract: BACKGROUND
  Cancer spread to the spine affects bone stability and can lead to pathologic fracture and neurologic impairment. Radiofrequency ablation (RFA) recently has gained popularity in treating skeletal tumors. Conventional RFA devices use a monopolar design, which limits the ability to comprehensively treat large tumors in bony tissues and may pose risks to adjacent critical normal neurologic tissues when applied to vertebrae. New bipolar-cooled radiofrequency (BCRF) may generate larger controlled lesions without the same degree of risk to adjacent structures.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the feasibility, efficacy, and safety of RFA with the use of a new bone-specific, BCRF probe in a porcine vertebral model and to evaluate the ability of magnetic resonance (MR) imaging to represent histologic outcomes of RFA treatment.
  
  
  METHODS
  Basic science: preclinical in vivo study.
  
  
  METHODS
  RFA was evaluated in three noncontiguous lumbar vertebrae in six Yorkshire pigs (25-30 kg). Via a transpedicular approach for probe placement, two vertebrae received BCRF treatment and one vertebrae served as a sham control. MR imaging and neurological assessments were conducted pre- and posttreatment as well as immediately before animal sacrifice (n=3 at day 0, n=3 at day 14). MR ablation zones were compared with hematoxylin and eosin-stained histological sections.
  
  
  RESULTS
  With BCRF, large reproducible zones of ablation were achieved, confined within the vertebrae, without damage to adjacent tissues or the spinal cord. All animals demonstrated normal consistent neurologic behavior pre- and posttreatment. External tissue temperatures around targeted vertebrae were not increased. MR imaging after 14 days was more effective in demonstrating ablation effects than images on day 0, with radiologic findings most apparent on T2-weighted sequences. Histologic analysis of samples corresponded well to the zones of ablation observed on MR images (R=0.9, p<.01).
  
  
  CONCLUSIONS
  The study demonstrated feasibility, safety, and effectiveness of BCRF ablation of vertebral bone. This motivates ongoing preclinical evaluation in diseased models to further explore the potential for its use in clinical treatment of metastatic vertebrae.
authors.affiliation: Institute of Biomaterials & Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON M5S 3G9, Canada; Sunnybrook Research Institute, 2075 Bayview Ave, Room S611, Toronto, ON M4N 3M5, Canada.
authors.forename: Padina S
authors.initials: PS
authors.lastname: Pezeshki
authors.affiliation: Baylis Medical Company, 2645 Matheson Blvd East, Mississauga, ON L4W 5S4, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Woo
authors.affiliation: Institute of Biomaterials & Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON M5S 3G9, Canada; Sunnybrook Research Institute, 2075 Bayview Ave, Room S611, Toronto, ON M4N 3M5, Canada.
authors.forename: Margarete K
authors.initials: MK
authors.lastname: Akens
authors.affiliation: Institute of Biomaterials & Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON M5S 3G9, Canada.
authors.forename: John E
authors.initials: JE
authors.lastname: Davies
authors.affiliation: Department of Anesthesia, St Michael's Hospital, 30 Bond St, Toronto, ON M5B 1W8, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Gofeld
authors.affiliation: Institute of Biomaterials & Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON M5S 3G9, Canada; Sunnybrook Research Institute, 2075 Bayview Ave, Room S611, Toronto, ON M4N 3M5, Canada.
authors.forename: Cari M
authors.initials: CM
authors.lastname: Whyne
authors.affiliation: Institute of Biomaterials & Biomedical Engineering, University of Toronto, Rosebrugh Building, 164 College Street, Room 407, Toronto, ON M5S 3G9, Canada; Sunnybrook Research Institute, 2075 Bayview Ave, Room S611, Toronto, ON M4N 3M5, Canada. Electronic address: albert.yee@sunnybrook.ca.
authors.forename: Albert J M
authors.initials: AJ
authors.lastname: Yee
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation* / Q000592:standards; D004195:Disease Models, Animal; D004867:Equipment Design; D005240:Feasibility Studies; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery; D011897:Random Allocation; D013125:Spinal Neoplasms / Q000556:secondary / Q000601:surgery*; D013552:Swine
keywords: Bone cancer; Bone metastases; Minimally invasive; Porcine; Preclinical; Radiofrequency ablation; Tumor