title: A sensitive method for measuring spatial orientation in bone structures.
abstract: OBJECTIVE
  This article introduces the newly developed line frequency deviation (LFD) method for measuring the orientation of the trabecular structure and shows that it is more sensitive than the mean intercept length (MIL) method that is commonly used.
  
  
  METHODS
  The LFD method, which has been developed to measure the orientation of bone on two-dimensional X-ray images, was expanded to handle three-dimensional shapes. For the purpose of comparison, both the LFD and the MIL methods were applied to micro CT scans of 24 trabecular bone samples as well as to 24 simple synthetic samples. LFD and MIL values were calculated in various directions and collected in polar plots. Next, the anisotropy was quantified by calculating the coefficient of variation as well as by fitting ellipsoids through the plots.
  
  
  RESULTS
  The MIL method yielded smooth rather spherical ellipsoidal polar plots with almost no sensitivity for changes in structure. The LFD method yielded more slender polar plots and more sensitivity for geometrical changes. The LFD method yielded significantly more anistropy and larger variation in anisotropy.
  
  
  CONCLUSIONS
  The LFD method is a more sensitive descriptor of spatial orientation of bone structures than the MIL method.
authors.affiliation: Department of Oral Radiology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands. WGeraets@ACTA.nl
authors.forename: W G M
authors.initials: WG
authors.lastname: Geraets
authors.forename: L J
authors.initials: LJ
authors.lastname: van Ruijven
authors.forename: J G C
authors.initials: JG
authors.lastname: Verheij
authors.forename: T M G J
authors.initials: TM
authors.lastname: van Eijden
authors.forename: P F
authors.initials: PF
authors.lastname: van der Stelt
mesh_terms: D016880:Anisotropy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008335:Mandibular Condyle / Q000000981:diagnostic imaging*; D008859:Microscopy, Polarization; D014057:Tomography, X-Ray Computed / Q000379:methods*