title: Diffusion weighted MRI of osteoid osteomas: Higher ADC values after radiofrequency ablation.
abstract: OBJECTIVE
  Feasibility of diffusion weighted MRI (DWI) pre- and post-radiofrequency ablation (RFA) in patients with osteoid osteoma (OO).
  
  
  METHODS
  Ten patients (1 female, 24±9years) received RFA of OO (mean size 8.7±3.2mm). Two OO recurred, in one of these a second RFA was performed. A 1.5T DWI (b=50, 400, and 800s/mm(2)) and a fat saturated DCE MRI were obtained the day before and after RFA. In DWI, the mean apparent diffusion coefficient (ADC) was recorded. With DCE MRI, signal-to-noise ratio, contrast-to-noise ratio, absolute signal intensity (SI), relative SI, and SI ratio were documented. All parameters were compared pre- and post-RFA using paired Wilcoxon rank test.
  
  
  RESULTS
  ADC values were significantly higher post-ablation, 1.6±0.5μm(2)/ms versus 1.3±0.6μm(2)/ms (p<0.05). Perfusion was significantly reduced after ablation [SNR, CNR, SI, %SI, and SI OO/SI muscle]; post-RFA: 55±13, 27±20, 757±534, 102±16, and 1.6±0.2; pre-RFA: 88±37, 65±22, 1038±755, 226±51, and 2.0±0.5 (p<0.05).
  
  
  CONCLUSIONS
  DWI is feasible in OO. ADC values increased and contrast enhancement decreased after RFA of OO. This may be explained by RFA-induced necrosis and devascularization.
authors.affiliation: Philipps University of Marburg, Diagnostic and Interventional Radiology, Baldingerstraße 35043 Marburg, Germany. Electronic address: stephan.rheinheimer@klinikum-karlsruhe.de.
authors.forename: S
authors.initials: S
authors.lastname: Rheinheimer
authors.affiliation: Philipps University of Marburg, Diagnostic and Interventional Radiology, Baldingerstraße 35043 Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Görlach
authors.affiliation: Philipps University of Marburg, Diagnostic and Interventional Radiology, Baldingerstraße 35043 Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Figiel
authors.affiliation: Philipps University of Marburg, Diagnostic and Interventional Radiology, Baldingerstraße 35043 Marburg, Germany.
authors.forename: A H
authors.initials: AH
authors.lastname: Mahnken
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D017115:Catheter Ablation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D010017:Osteoma, Osteoid / Q000000981:diagnostic imaging* / Q000601:surgery*; D059629:Signal-To-Noise Ratio; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D055815:Young Adult
keywords: Diffusion; Dynamic contrast; MRI; Osteoid osteoma; Radiofrequency ablation; Recurrent