title: Nontraumatic osteonecrosis: MR perfusion imaging evaluation in an experimental model.
abstract: OBJECTIVE
  Because the nature and time course of changes in early, nontraumatic osteonecrosis at perfusion and magnetic resonance (MR) imaging are unknown, the authors evaluated this technique in the assessment of early osteonecrosis with a nontraumatic model.
  
  
  METHODS
  Five rabbits underwent intravenous injection of lipopolysaccharide endotoxin followed by intramuscular injection of methylprednisolone. MR imaging of the femora was performed before and at weekly intervals after endotoxin injection. Histologic findings from the areas of osteonecrosis were correlated with the findings of MR imaging and MR perfusion studies.
  
  
  RESULTS
  Histologic evaluation showed osteonecrosis in six femora of four animals 2-4 weeks after endotoxin injection. Findings on T1-weighted images of the femur were normal in all animals; T2-weighted images of one femur showed equivocal changes. On MR perfusion images, the baseline mean peak percentage of enhancement was 52.7% +/- 12.6. In the six areas without osteonecrosis, the mean percentage of enhancement was similar to the baseline percentage of enhancement at 1 week (62.2% +/- 31.2). In the four areas with diffuse osteonecrosis, there was essentially no contrast enhancement 1-4 weeks after endotoxin injection.
  
  
  CONCLUSIONS
  T1- and T2-weighted MR imaging is insensitive to the presence of early nontraumatic osteonecrosis. MR perfusion imaging might be useful to detect early nontraumatic osteonecrosis.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA.
authors.forename: S
authors.initials: S
authors.lastname: Kawamoto
authors.forename: N
authors.initials: N
authors.lastname: Shirai
authors.forename: J D
authors.initials: JD
authors.lastname: Strandberg
authors.forename: J L
authors.initials: JL
authors.lastname: Boxerman
authors.forename: D A
authors.initials: DA
authors.lastname: Bluemke
mesh_terms: D000818:Animals; D003287:Contrast Media; D004926:Escherichia coli; D005269:Femur / Q000473:pathology; D019786:Gadolinium DTPA; D008070:Lipopolysaccharides; D008279:Magnetic Resonance Imaging; D010020:Osteonecrosis / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D011817:Rabbits
chemical_list: D003287:Contrast Media; D008070:Lipopolysaccharides; D019786:Gadolinium DTPA