title: Validity and reliability of computerized measurement of lumbar intervertebral disc height and volume from magnetic resonance images.
abstract: BACKGROUND
  Magnetic resonance (MR) examinations of morphologic characteristics of intervertebral discs (IVDs) have been used extensively for biomechanical studies and clinical investigations of the lumbar spine. Traditionally, the morphologic measurements have been performed using time- and expertise-intensive manual segmentation techniques not well suited for analyses of large-scale studies..
  
  
  OBJECTIVE
  The purpose of this study is to introduce and validate a semiautomated method for measuring IVD height and mean sagittal area (and volume) from MR images to determine if it can replace the manual assessment and enable analyses of large MR cohorts.
  
  
  METHODS
  This study compares semiautomated and manual measurements and assesses their reliability and agreement using data from repeated MR examinations.
  
  
  METHODS
  Seven healthy asymptomatic males underwent 1.5-T MR examinations of the lumbar spine involving sagittal T2-weighted fast spin-echo images obtained at baseline, pre-exercise, and postexercise conditions. Measures of the mean height and the mean sagittal area of lumbar IVDs (L1-L2 to L4-L5) were compared for two segmentation approaches: a conventional manual method (10-15 minutes to process one IVD) and a specifically developed semiautomated method (requiring only a few mouse clicks to process each subject).
  
  
  RESULTS
  Both methods showed strong test-retest reproducibility evaluated on baseline and pre-exercise examinations with strong intraclass correlations for the semiautomated and manual methods for mean IVD height (intraclass correlation coefficient [ICC]=0.99, 0.98) and mean IVD area (ICC=0.98, 0.99), respectively. A bias (average deviation) of 0.38 mm (4.1%, 95% confidence interval 0.18-0.59 mm) was observed between the manual and semiautomated methods for the IVD height, whereas there was no statistically significant difference for the mean IVD area (0.1%±3.5%). The semiautomated and manual methods both detected significant exercise-induced changes in IVD height (0.20 and 0.28 mm) and mean IVD area (5.7 and 8.3 mm(2)), respectively.
  
  
  CONCLUSIONS
  The presented semiautomated method provides an alternative to time- and expertise-intensive manual procedures for analysis of larger, cross-sectional, interventional, and longitudinal MR studies for morphometric analyses of lumbar IVDs.
authors.affiliation: The Australian E-Health Research Centre, CSIRO Computational Informatics, Brisbane, Australia; School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia.
authors.forename: Ales
authors.initials: A
authors.lastname: Neubert
authors.affiliation: The Australian E-Health Research Centre, CSIRO Computational Informatics, Brisbane, Australia.
authors.forename: Jurgen
authors.initials: J
authors.lastname: Fripp
authors.affiliation: School of Human Movement Studies, University of Queensland, Brisbane, Australia.
authors.forename: Craig
authors.initials: C
authors.lastname: Engstrom
authors.affiliation: School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia.
authors.forename: Yaniv
authors.initials: Y
authors.lastname: Gal
authors.affiliation: School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia.
authors.forename: Stuart
authors.initials: S
authors.lastname: Crozier
authors.affiliation: Exercise Physiology, La Trobe Rural Health School, La Trobe University, Victoria 3550, Australia. Electronic address: m.kingsley@latrobe.edu.au.
authors.forename: Michael I C
authors.initials: MI
authors.lastname: Kingsley
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009929:Organ Size; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Computerized measurement; Intervertebral disc; Magnetic resonance imaging; Morphometry; Reproducibility; Spinal shrinkage