title: Osteoid osteoma in atypical locations: the added value of dynamic gadolinium-enhanced MR imaging.
abstract: OBJECTIVE
  To compare the results of dynamic gadolinium-enhanced magnetic resonance imaging (MRI), unenhanced MRI and computed tomography (CT), in terms of nidus conspicuity and diagnostic confidence of osteoid osteoma in atypical sites.
  
  
  METHODS
  CT and MR (nonenhanced T1- and T2-weighted and dynamic MRI) images of 19 patients with histologically proven osteoid osteoma located in atypical sites were retrospectively reviewed. Time-enhancement curves of the nidus and the adjacent bone marrow were generated. Images from each technique were scored for nidus conspicuity by two independent radiologists. Another blinded radiologist was asked to assess final diagnosis of the bone lesion on MR and CT images, independently.
  
  
  RESULTS
  In all cases, nidus contrast uptake started in the arterial phase and was higher compared to the surrounding bone marrow. Dynamic MRI significantly increased nidus conspicuity compared to nonenhanced MRI (P<.0001) and CT (P=.04). In 6/19 (31.6%) cases nidus conspicuity was higher at dynamic MRI compared to CT. Confident diagnosis of osteoid osteoma was achieved in all patients with MRI and in 10/19 (52.6%) patients with CT.
  
  
  CONCLUSIONS
  In patients with osteoid osteoma located in atypical sites, dynamic MRI increases nidus conspicuity, allowing confident diagnosis.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Pisa, Via Roma 56, 56126 Pisa, Italy. virnazampa@hotmail.com
authors.forename: Virna
authors.initials: V
authors.lastname: Zampa
authors.forename: Irene
authors.initials: I
authors.lastname: Bargellini
authors.forename: Simona
authors.initials: S
authors.lastname: Ortori
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Faggioni
authors.forename: Roberto
authors.initials: R
authors.lastname: Cioni
authors.forename: Carlo
authors.initials: C
authors.lastname: Bartolozzi
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000175:diagnosis*; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010017:Osteoma, Osteoid / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D005682:Gadolinium