title: Low-dose three-dimensional reconstruction of the femur with unit free-form deformation.
abstract: OBJECTIVE
  This paper describes a low-dose method for reconstructing three-dimensional models of femur, using a standard shape model (SSM) and two conventional x-ray images.
  
  
  METHODS
  The x-ray images were taken in two orthogonal directions. The x-ray source and sensor configurations were documented. An optimized algorithm was employed to align the x-ray image to the three-dimensional model. A method of direct correspondence building is proposed for linking two-dimensional images with three-dimensional projections of a SSM. The reconstruction method proposed in this paper is based on a SSM, which was adapted for x-ray images of individual bones. The adaption was executed by deforming the template bone shape until its silhouette boundary exactly matched the x-ray image of the individual bone. A silhouette-based unit free-form deformation method was evaluated for its suitability in the adaption of the SSM for x-ray images. Comprehensive experiments were designed and conducted for 35 specimens.
  
  
  RESULTS
  The validity of the low-dose reconstruction method was demonstrated for the femur, with good results for accuracy (mean error of 1.1 mm, root-mean-square error of 2.1 mm), reproducibility (intraobservation coefficient of variation of 1.1%, interobservation coefficient of variation of 1.4%), and time consumption (mean of 5 min for a full femur).
  
  
  CONCLUSIONS
  Once this approach has been validated in vivo, it should be suited to multiple applications of routine clinical and research practices.
authors.affiliation: Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Xiangsen
authors.initials: X
authors.lastname: Zeng
authors.affiliation: Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Chentao
authors.initials: C
authors.lastname: Wang
authors.affiliation: Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Wei
authors.affiliation: Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Chen
mesh_terms: D000328:Adult; D000465:Algorithms; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011859:Radiography; D015203:Reproducibility of Results; D013995:Time