title: Quantification of lumbar intradiscal deformation during flexion and extension, by mathematical analysis of magnetic resonance imaging pixel intensity profiles.
abstract: METHODS
  A magnetic resonance imaging study of the internal kinematic response of normal lumbar intervertebral discs to non-weight-bearing flexion and extension.
  
  
  OBJECTIVE
  To quantify the pattern of magnetic resonance imaging pixel intensity variation across discs, and noninvasively monitor displacement of the nucleus pulposus during sagittal-plane movements.
  
  
  BACKGROUND
  Invasive techniques used to study intradiscal movements of the nucleus pulposus have suggested that it moves posteriorly during flexion and anteriorly during extension. A noninvasive study based on magnetic resonance images gave similar results for normal young women. Quantification has been problematic, and the invasive procedures may have altered disc dynamics.
  
  
  METHODS
  Ten male subjects (age, 21-38 years) with healthy backs were positioned in a magnetic resonance imaging portal with their lumbar spine stabilized in flexion and extension by supporting pads. For each disc, a T2-weighted image was obtained, as was a computer-generated profile of pixel intensities along a horizontal mid-discal transect. Mathematical curve-fitting regression analysis was used to characterize the shape of the intensity profile and to compute the point of maximum pixel intensity.
  
  
  RESULTS
  A single equation fitted the profile for all normal discs. The intensity peak shifted posteriorly during flexion, anteriorly during extension.
  
  
  CONCLUSIONS
  Automated mathematical modeling of magnetic resonance imaging pixel data can be used to describe the fundamental shape of the pixel intensity profile across a normal lumbar disc, to determine the precise location of the site of maximum pixel intensity, and to measure the movement of this peak with flexion and extension. This technique may be of value in recognizing incipient degenerative changes in lumbar discs.
authors.affiliation: Department of Radiology, Midwestern University, Chicago, Illinois, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Brault
authors.forename: D M
authors.initials: DM
authors.lastname: Driscoll
authors.forename: L L
authors.initials: LL
authors.lastname: Laakso
authors.forename: R E
authors.initials: RE
authors.lastname: Kappler
authors.forename: E F
authors.initials: EF
authors.lastname: Allin
authors.forename: T
authors.initials: T
authors.lastname: Glonek
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007403:Intervertebral Disc / Q000502:physiology*; D007700:Kinetics; D008159:Lumbar Vertebrae / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D016059:Range of Motion, Articular