title: Percutaneous MR imaging-guided radiofrequency interstitial thermal ablation of tongue base in porcine models: implications for obstructive sleep apnea syndrome.
abstract: OBJECTIVE
  To test the feasibility and safety of a percutaneous magnetic resonance (MR) imaging-guided technique for radiofrequency (RF) interstitial thermal ablation of the tongue base and to correlate MR appearance of induced thermal lesions with histopathologic findings in pigs in acute and chronic porcine models.
  
  
  METHODS
  A 1-cm-tip RF electrode was inserted percutaneously into the tongue in 10 pigs with 0.2-T real-time MR guidance. The RF electrode was advanced up the midline between lingual arteries and stopped short of tongue mucosa. RF interstitial thermal ablation was performed at 90 degrees C +/- 2 and lasted 10 minutes. Postablation images were obtained with a 1.5-T MR imager. Five pigs were sacrificed immediately (acute model), while five were followed up for 1 month (chronic model) before they were sacrificed. MR-compatible fiducial coils were inserted into tongues with MR imaging guidance prior to RF ablation in the chronic group. Tongues were harvested for histopathologic analysis. Mean thermal lesion volume was compared with the Student t test on images obtained immediately, 2 weeks, and 1 month after RF ablation. Interclass correlation coefficients of lesion diameters at gross pathologic analysis and corresponding diameters with each pulse sequence were calculated.
  
  
  RESULTS
  Successful MR imaging-guided electrode positioning was achieved in all procedures without intra- or postprocedure complications because there was high vascular conspicuity and tissue contrast. Thermal lesions appeared hypointense with hyperintense surrounding rims with all sequences in both groups. At pathologic analysis, acute lesions appeared as pale necrotic areas surrounded by hyperemic rims, while chronic lesions demonstrated progressive circumferential fibrosis and significant volume shrinkage (P <.01). Thermal lesion diameters measured at gross pathologic analysis best agreed with corresponding diameters measured on short inversion time inversion-recovery images (interclass correlation coefficient = 0.85).
  
  
  CONCLUSIONS
  The results of this investigation demonstrate MR imaging-guided RF interstitial thermal ablation of the tongue base is feasible and safe and illustrate imaging and pathologic phenomena associated with creation and evolution of the induced thermal lesions.
authors.affiliation: Dept of Radiology, Univ Hosp of Cleveland/Case Western Reserve Univ School of Med, 11100 Euclid Ave, Cleveland, OH 44106-5056, USA.
authors.forename: Sherif Gamal
authors.initials: SG
authors.lastname: Nour
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lewin
authors.forename: Michael
authors.initials: M
authors.lastname: Gutman
authors.forename: Claudia
authors.initials: C
authors.lastname: Hillenbrand
authors.forename: Frank K
authors.initials: FK
authors.lastname: Wacker
authors.forename: John W
authors.initials: JW
authors.lastname: Wong
authors.forename: Ian C
authors.initials: IC
authors.lastname: Mitchell
authors.forename: Charles B
authors.initials: CB
authors.lastname: Armstrong
authors.forename: Mufaddal M
authors.initials: MM
authors.lastname: Hashim
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Duerk
authors.forename: Melvin
authors.initials: M
authors.lastname: Strauss
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005240:Feasibility Studies; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D020181:Sleep Apnea, Obstructive / Q000628:therapy*; D013552:Swine; D013813:Therapy, Computer-Assisted / Q000295:instrumentation*; D014059:Tongue / Q000473:pathology; D016896:Treatment Outcome; D014945:Wound Healing / Q000502:physiology