title: Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible.
abstract: OBJECTIVE
  The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible.
  
  
  METHODS
  Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 μm voxel size and cone beam CT (CBCT) with 200 μm, 300 μm, and 400 μm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low(5)) and high (High(5)) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed.
  
  
  RESULTS
  The alveolar bone region had significantly lower Mean, Low(5) and High(5) values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05).
  
  
  CONCLUSIONS
  CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.
authors.affiliation: Division of Orthodontics, College of Dentistry, Ohio State University. Columbus, OH 43210-1267, USA.
authors.forename: T T
authors.initials: TT
authors.lastname: Taylor
authors.forename: S I
authors.initials: SI
authors.lastname: Gans
authors.forename: E M
authors.initials: EM
authors.lastname: Jones
authors.forename: A R
authors.initials: AR
authors.lastname: Firestone
authors.forename: W M
authors.initials: WM
authors.lastname: Johnston
authors.forename: D-G
authors.initials: DG
authors.lastname: Kim
mesh_terms: D000465:Algorithms; D015519:Bone Density; D002102:Cadaver; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation; D006801:Humans; D008334:Mandible / Q000000981:diagnostic imaging*; D015898:Tomography Scanners, X-Ray Computed; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods; D055114:X-Ray Microtomography / Q000295:instrumentation