title: 3D femur model reconstruction from biplane X-ray images: a novel method based on Laplacian surface deformation.
abstract: OBJECTIVE
  Conventional methods for 3D bone model reconstruction from CT scans can require high-radiation dose, cost and time. A 3D model generated from 2D X-ray images may be a useful alternative. Reconfiguring a 3D template surface mesh model to match bone shape in orthogonal radiographs is a common technique for 3D reconstruction. A computationally efficient 3D bone modeling algorithm was developed and tested.
  
  
  METHODS
  An algorithm for bone template reconfiguration is proposed, which uses Kohonen self-organizing maps for 2D-3D correspondence between input X-ray images and the template. Laplacian surface deformation is then used for final deformation of the template. In the literature, Laplacian deformation has been shown to perform better than thin-plate splines and free form deformation in terms of computation time and mesh quality. The method was applied to 22 sets of simulated input contours generated from 3D models of the distal femur.
  
  
  RESULTS
  An acceptable range of reconstruction error: 1.5 mm of RMS-P2S (root-mean-square point-to-surface) distance and 1.2 mm mean-P2S distance errors was observed based on comparison with the corresponding reference models/ground truth. Computation time for the 3D bone modeling algorithm was less than a minute for each case.
  
  
  CONCLUSIONS
  The new template reconfiguration algorithm based on Laplacian surface deformation provided acceptable reconstruction accuracy and high computation efficiency for 3D modeling of the distal femur using biplane radiographs. This algorithm may provide a useful option for orthopedic modeling applications.
authors.affiliation: OrthoCAD Lab, Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, Maharashtra, India, vicky731@gmail.com.
authors.forename: Vikas
authors.initials: V
authors.lastname: Karade
authors.forename: Bhallamudi
authors.initials: B
authors.lastname: Ravi
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008954:Models, Biological; D014057:Tomography, X-Ray Computed / Q000379:methods