title: High precision semiautomated computed tomography measurement of lumbar disk and vertebral heights.
abstract: OBJECTIVE
  Evaluation of treatments of many spine disorders requires precise measurement of the heights of vertebral bodies and disk spaces. The authors present a semiautomated computer algorithm measuring those heights from spine computed tomography (CT) scans and evaluate its precision.
  
  
  METHODS
  Eight patients underwent two spine CT scans in the same day. In each scan, five thoracolumbar vertebral heights and four disk heights were estimated using the algorithm. To assess precision, the authors computed the differences between the height measurements in the two scans, coefficients of variation (CV), and 95% limits of agreement. Intraoperator and interoperator precisions were evaluated. For local vertebral and disk height measurement (anterior, middle, posterior) the algorithm was compared to a manual mid-sagittal plane method.
  
  
  RESULTS
  The mean (standard deviation) interscan difference was as low as 0.043 (0.031) mm for disk heights and 0.044 (0.043) mm for vertebral heights. The corresponding 95% limits of agreement were [-0.085, 0.11] and [-0.10, 0.12] mm, respectively. Intraoperator and interoperator precision was high, with a maximal CV of 0.30%. For local vertebral and disk heights, the algorithm improved upon the precision of the manual mid-sagittal plane measurement by as much as a factor of 6 and 4, respectively.
  
  
  CONCLUSIONS
  The authors evaluated the precision of a novel computer algorithm for measuring vertebral body heights and disk heights using short term repeat CT scans of patients. The 95% limits of agreement indicate that the algorithm can detect small height changes of the order of 0.1 mm.
authors.affiliation: National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Sovira
authors.initials: S
authors.lastname: Tan
authors.forename: Jianhua
authors.initials: J
authors.lastname: Yao
authors.forename: Lawrence
authors.initials: L
authors.lastname: Yao
authors.forename: Michael M
authors.initials: MM
authors.lastname: Ward
mesh_terms: D000328:Adult; D000368:Aged; D001331:Automation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D016011:Normal Distribution; D015588:Observer Variation; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*