title: A method for quantifying intervertebral disc signal intensity on T2-weighted imaging.
abstract: BACKGROUND
  Quantification of intervertebral disc degeneration based on intensity of the nucleus pulposus in magnetic resonance imaging (MRI) often uses the mean intensity of the region of interest (ROI) within the nucleus pulposus. However, the location and size of ROI have varied in different reports, and none of the reported methods can be considered fully objective.
  
  
  OBJECTIVE
  To develop a more objective method of establishing ROIs for quantitative evaluation of signal intensity in the nucleus pulposus using T2-weighted MRI.
  
  
  METHODS
  A 1.5-T scanner was used to obtain T2-weighted mid-sagittal images. A total of 288 intervertebral discs from 48 patients (25 men, 23 women) were analyzed. Mean age was 47.4 years (range, 17-69 years). All discs were classified into five grades according to Pfirrmann et al. Discs in grades I and II were defined as bright discs, and discs in grades IV and V were defined as dark discs. Eight candidate methods of ROI determination were devised. The method offering the highest degree of discrimination between bright and dark discs was investigated among these eight methods.
  
  
  RESULTS
  The method with the greatest degree of discrimination was as follows. The quadrangle formed by anterior and posterior edges of the upper and lower end plates in contact with the intervertebral disc to be measured was defined as the intervertebral area. A shape similar to the intervertebral area but with one-quarter the area was drawn. The geometrical center of the shape was matched to the center of intensity, and this shape was then used as the ROI. Satisfactory validity and reproducibility were obtained using this method.
  
  
  CONCLUSIONS
  The present method offers adequate discrimination and could be useful for longitudinal tracking of intervertebral disc degeneration with sufficient reproducibility.
authors.affiliation: Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nagashima
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Abe
authors.forename: Kenji
authors.initials: K
authors.lastname: Amaya
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yanaihara
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishiwaki
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
authors.forename: Morio
authors.initials: M
authors.lastname: Matsumoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis* / Q000473:pathology; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012984:Software