title: [Relationship between the gray level of X-ray photograph and the cortical thickness].
abstract: OBJECTIVE
  In order to get three dimensional measurements simply an plain X-ray photographs.
  
  
  METHODS
  The multi-layers of bone pieces were made by use of bone saw, and piled up to spiral ladder, which was used as a calibrating module for to living bone in clinics. The relationship between the cortical thickness and gray level of the X-ray photographs was obtained.
  
  
  RESULTS
  The correlation can be described with a cubic regression curve, and it can be simplified to a linear regression equation when cortical thickness is small than 3.8 mm.
  
  
  CONCLUSIONS
  It can be realized to get three dimensional measures of the bone on plain X-ray photographs, by use of the bony spiral ladder described here.
authors.affiliation: College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100022, China.
authors.forename: Hong-gang
authors.initials: HG
authors.lastname: Zhong
authors.forename: Hai-bin
authors.initials: HB
authors.lastname: Bu
authors.forename: Fu-hui
authors.initials: FH
authors.lastname: Dong
mesh_terms: D000328:Adult; D001842:Bone and Bones / Q000737:chemistry* / Q000000981:diagnostic imaging*; D006801:Humans; D011859:Radiography; D014965:X-Rays