title: Ionic versus nonionic paramagnetic contrast media in differentiating between scar and herniated disk.
abstract: OBJECTIVE
  To compare the MR contrast enhancement produced by ionic and nonionic paramagnetic contrast media in herniated disk fragments with that in epidural scar tissue.
  
  
  METHODS
  A recurrent herniated disk was modeled in canines by using laminectomy to place a fragment of disk cartilage in the epidural space. The dogs were studied 88 and 90 days after laminectomy with MR imaging enhanced with an ionic or a nonionic paramagnetic contrast medium. Contrast enhancement of the epidural scar tissue and the epidural disk fragment was measured at 2, 22, and 45 minutes after the injection.
  
  
  RESULTS
  Contrast enhancement was consistently and significantly higher in scar tissue than in disk fragments, although the difference decreased between 2 and 45 minutes after administration of contrast medium. Enhancement of disk fragments was less with the ionic than with the nonionic contrast medium. Contrast between the disk fragments and scar was also greater with the ionic than with the nonionic medium.
  
  
  CONCLUSIONS
  The contrast between recurrent disk fragments and scar tissue is affected by the timing of the scan and the choice of contrast medium. Scans obtained immediately after the injection of contrast medium show more contrast between disk fragment and scar than do delayed scans. Recurrent herniated disk fragments are more effectively shown by ionic than by nonionic media.
authors.affiliation: Department of Radiology, Medical College of Wisconsin, Milwaukee, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Nguyen
authors.forename: K C
authors.initials: KC
authors.lastname: Ho
authors.forename: H
authors.initials: H
authors.lastname: An
authors.forename: L H
authors.initials: LH
authors.lastname: Riley
authors.forename: X
authors.initials: X
authors.lastname: Rongming
authors.forename: V M
authors.initials: VM
authors.lastname: Haughton
mesh_terms: D000818:Animals; D002921:Cicatrix / Q000175:diagnosis*; D003287:Contrast Media; D003937:Diagnosis, Differential; D004285:Dogs; D004824:Epidural Space; D007405:Intervertebral Disc Displacement / Q000175:diagnosis*; D007477:Ions; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D013122:Spinal Diseases / Q000175:diagnosis*
chemical_list: D003287:Contrast Media; D007477:Ions