title: MR-guided high-focused ultrasound for renal sympathetic denervation-a feasibility study in pigs.
abstract: BACKGROUND
  Renal sympathetic denervation has recently gained clinical relevance for the treatment of therapy-resistant hypertension. Denervation is currently mainly performed using catheter-based transarterial radiofrequency ablation of periarterial sympathetic nerve fibers. Since this approach has numerous limitations, we conducted a study to evaluate the feasibility, safety, and efficacy of magnetic resonance-guided high-focused ultrasound (MRgHiFUS) for renal sympathetic denervation in pigs as an alternative to catheter-based ablation.
  
  
  METHODS
  Renal periarterial MRgHiFUS was performed under general anesthesia in ten pigs. Blood pressure measurements and magnetic resonance imaging (MRI) of the kidneys, renal arteries, and surrounding structures were obtained immediately before and after the interventions and after 4 weeks. Histological examinations of periarterial tissues and determination of renal norepinephrine (NE) concentration were performed to assess treatment efficacy.
  
  
  CONCLUSIONS
  In each pig, 9.8 ± 2.6 sonications with a mean energy deposition of 2,670 ± 486 J were performed. The procedure was well tolerated by all pigs. No major complications occurred. MRgHiFUS induced periarterial edema in three pigs, but only one pig showed corresponding histological changes. The NE level of the treated kidney was lower in five pigs (-8% to -38%) compared to the untreated side. Overall, there was no significant difference between the NE values of both kidneys in any of the treated pigs. Postinterventional MRI indicated absorption of ultrasound energy at the transverse process and fascia.
  
  
  CONCLUSIONS
  MRgHiFUS had some thermal periarterial effects but failed to induce renal denervation. Insufficient energy deposition is most likely attributable to a small acoustic window with beam path impediment in the porcine model. Since HiFUS treatment in humans is expected to be easier to perform due to better access to renal sympathetic nerves, further studies of this method are desirable to investigate the potential of MRgHiFUS as an alternative for patients not suitable for catheter-based renal sympathicolysis.
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Freyhardt
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Lilian
authors.initials: L
authors.lastname: Heckmann
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Beck
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Nicola
authors.initials: N
authors.lastname: Stolzenburg
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Schnorr
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Kamp
authors.affiliation: Department of Neuropathology, Charité - Universitätsmedizin Berlin, Berlin 13353, Germany.
authors.forename: Jan L
authors.initials: JL
authors.lastname: Rinnenthal
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Günther
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin 13353, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Streitparth
keywords: Hypertension; MRgHiFUS sympathicolysis; Renal sympathetic denervation