title: Magnetic resonance-guided focused ultrasound treatment of facet joint pain: summary of preclinical phase.
abstract: METHODS
  A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted to test the feasibility, safety, and efficacy of magnetic resonance-guided focused ultrasound (MRgFUS) for treating facet joint pain.
  
  
  OBJECTIVE
  The goal of the current study was to develop a novel method for accurate and safe noninvasive facet joint ablation using MRgFUS.
  
  
  BACKGROUND
  Facet joints are a common source of chronic back pain. Direct facet joint interventions include medial branch nerve ablation and intra-articular injections, which are widely used, but limited in the short and long term. MRgFUS is a breakthrough technology that enables accurate delivery of high-intensity focused ultrasound energy to create a localized temperature rise for tissue ablation, using MR guidance for treatment planning and real-time feedback.
  
  
  METHODS
  We validated the feasibility, safety, and efficacy of MRgFUS for facet joint ablation using the ExAblate 2000® System (InSightec Ltd., Tirat Carmel, Israel) and confirmed the system's ability to ablate the edge of the facet joint and all terminal nerves innervating the joint. A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted.
  
  
  RESULTS
  The experiments showed that targeting the facet joint with energies of 150-450 J provides controlled and accurate heating at the facet joint edge without penetration to the vertebral body, spinal canal, or root foramina. Treating with reduced diameter of the acoustic beam is recommended since a narrower beam improves access to the targeted areas.
  
  
  CONCLUSIONS
  MRgFUS can safely and effectively target and ablate the facet joint. These results are highly significant, given that this is the first study to demonstrate the potential of MRgFUS to treat facet joint pain.
authors.affiliation: Department of Neurological Surgery, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Sagi
authors.initials: S
authors.lastname: Harnof
authors.affiliation: Department of Neurological Surgery, Sheba Medical Center, Ramat Gan 52621, Israel.|Department of Neurological Surgery, The Ohio State University Medical Center, Columbus, OH 43210, USA.
authors.forename: Zion
authors.initials: Z
authors.lastname: Zibly
authors.affiliation: Department of Neurological Surgery, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Lilach
authors.initials: L
authors.lastname: Shay
authors.affiliation: Department of Neurological Surgery, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Osnat
authors.initials: O
authors.lastname: Dogadkin
authors.affiliation: The Focus Ultrasound Foundation, Charlottesville, VA 22903, USA.
authors.forename: Arik
authors.initials: A
authors.lastname: Hanannel
authors.affiliation: Department of Radiology, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Inbar
authors.affiliation: Department of Anesthesiology, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Itay
authors.initials: I
authors.lastname: Goor-Aryeh
authors.affiliation: Department of Orthopedic Surgery, Sheba Medical Center, Ramat Gan 52621, Israel.
authors.forename: Israel
authors.initials: I
authors.lastname: Caspi
keywords: Chronic back pain; Facet joints; MRgFUS; Pain palliation