title: Lesion formation in radiofrequency surgery of the tongue base.
abstract: OBJECTIVE
  Temperature controlled radiofrequency volumetric tissue reduction (RFVTR) of the tongue base is a minimally invasive technique for the treatment of obstructive sleep apnea. But despite its widespread use, little is yet known about in vivo effects in humans. Such knowledge would be essential for evidence-based criteria in the selection of energy application.
  
  
  METHODS
  In a preparatory in vitro study, porcine tongues were preserved in growing medium. Lesions with different amounts of energy were applied, and maximum diameters were assessed. In the in vivo study, 11 patients were treated with RFVTR at the tongue base by employing different energy levels (800, 600, 400, or 200 J) on two application sites. Magnetic resonance imagery scans were performed 4 to 6, 8 to 10, and 24 hours after surgery. An inversion recovery technique was used to visualize the lesions.
  
  
  RESULTS
  RFVTR created lesions at the porcine tongue from 50 J and higher. Maximum lesion sizes were achieved with 400 J. In vivo, all the lesions were clearly visible in the postoperative scans. Lesion size increased with the amount of energy applied. Maximum diameters were created from 600 J and higher. Higher amounts of energy only resulted in a slight increase in lesion length.
  
  
  CONCLUSIONS
  The application of 600 J at 85 degrees C leads to optimal lesion sizes. Higher amounts of energy will not lead to a relevant increase in tissue necrosis. With regard to the time needed for application, 600 J appears to be the ideal adjustment for energy delivery in the treatment of the human tongue.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University Hospital Mannheim, Germany. boris.stuck@hno.ma.uni-heidelberg.de
authors.forename: Boris A
authors.initials: BA
authors.lastname: Stuck
authors.forename: Julian
authors.initials: J
authors.lastname: Köpke
authors.forename: Joachim T
authors.initials: JT
authors.lastname: Maurer
authors.forename: Thomas
authors.initials: T
authors.lastname: Verse
authors.forename: Andreas
authors.initials: A
authors.lastname: Eckert
authors.forename: Gregor
authors.initials: G
authors.lastname: Bran
authors.forename: Christoph
authors.initials: C
authors.lastname: Düber
authors.forename: Karl
authors.initials: K
authors.lastname: Hörmann
mesh_terms: D000402:Airway Obstruction / Q000473:pathology / Q000628:therapy; D000818:Animals; D019317:Evidence-Based Medicine; D006801:Humans; D006979:Hyperthermia, Induced; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D008432:Mathematical Computing; D020181:Sleep Apnea, Obstructive / Q000473:pathology / Q000628:therapy; D013552:Swine; D014059:Tongue / Q000473:pathology*