title: Effect of exposure parameters and voxel size on bone structure analysis in CBCT.
abstract: OBJECTIVE
  To evaluate the effect of exposure parameters and voxel size on bone structure analysis in dental CBCT.
  
  
  METHODS
  20 cylindrical bone samples underwent CBCT scanning (3D Accuitomo 170; J. Morita, Kyoto, Japan) using three combinations of tube voltage (kV) and tube current-exposure time product (mAs), corresponding with a CT dose index of 3.4 mGy: 90 kV and 62 mAs, 73 kV and 108.5 mAs, and 64 kV and 155 mAs. Images were reconstructed with a voxel size of 0.080 mm. In addition, the 90 kV scan was reconstructed at voxel sizes of 0.125, 0.160, 0.200, 0.250 and 0.300 mm. The following parameters were measured: bone surface (BS) and bone volume (BV) per total volume (TV), fractal dimension, connectivity density, anisotropy, trabecular thickness (Tb. Th.) and trabecular spacing (Tb. Sp.), structure model index (SMI), plateness, branches, junctions, branch length and triple points.
  
  
  RESULTS
  For most parameters, there was no significant effect of the kV value. For BV/TV, "90 kV" differed significantly from the other kV settings; for SMI, "64 vs 73 kV" was significant. For BS/TV, fractal dimension, connectivity density, branches, junctions and triple points values incrementally decreased at larger voxel sizes, whereas an increase was seen for Tb. Th., Tb. Sp., SMI and branch length. For anisotropy and plateness, no (or little) effect of voxel size was seen; for BV/TV, the effect was inconsistent.
  
  
  CONCLUSIONS
  Most bone structure parameters are not affected by the kV if the radiation dose is constant. Parameters dealing with the trabecular structure are heavily affected by the voxel size.
authors.affiliation: 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.|2 OMFS-IMPATH Research Group, Oral Imaging Center, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Pauwels
authors.affiliation: 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: T
authors.initials: T
authors.lastname: Faruangsaeng
authors.affiliation: 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: T
authors.initials: T
authors.lastname: Charoenkarn
authors.affiliation: 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Ngonphloy
authors.affiliation: 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: S
authors.initials: S
authors.lastname: Panmekiate
mesh_terms: D016880:Anisotropy; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D017709:Fractals; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008334:Mandible; D009929:Organ Size; D011829:Radiation Dosage; D013997:Time Factors
keywords: bone quality; computer-assisted image processing; cone beam CT; trabecular bone