Difference between revisions of "Mapped Hexahedral Meshing"

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'''Progress:'''
 
'''Progress:'''
 
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* Previous work on this project was performed at the 2007 AHM -  [https://na-mic.org/w/images/3/34/2007_AHM_Programming_Half_Week_MappedMesh.ppt Mapped Mesh 4 Block]
 
* Warped meshing framework has been developed using VTK and ITK using a finite element approach
 
* Warped meshing framework has been developed using VTK and ITK using a finite element approach
 
**VTK
 
**VTK
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***Mesh quality
 
***Mesh quality
  
* Meshing module is now built by default with Slicer3
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'''Publications:'''
'''To Do:'''
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*Grosland NM, Bafna R, Magnotta VA. [http://www.informaworld.com/smpp/content~db=all?content=10.1080/10255840802136143 Automated hexahedral meshing of anatomic structures using deformable registration]. Comput Methods Biomech Biomed Engin. 12(1):35-43, 2009.
* We should remove the need for the surface extraction when Slicer3 supports the loading of unstructured grids.
 
  
 
'''Key Investigators:'''
 
'''Key Investigators:'''
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'''Links:'''
 
'''Links:'''
*[http://www.ccad.uiowa.edu/mimx Musculoskeletal Imaging, Modelling and Experimentation (MIMX)]
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*[http://www.ccad.uiowa.edu/mimx Musculoskeletal Imaging, Modeling and Experimentation (MIMX)]
  
'''Description:'''
 
This program will convert an image into a hexahedral mesh using
 
the voxels as the hexahedral elements. This is is typically done
 
for only a portion of the image and thus a binary image from a
 
segmentation may be used to define the region for meshing.
 
Since these meshes may be fairly large the user is allowed
 
to downsample the image by an integer value. Currently this
 
must be odd.
 
  
This tool was developed as part of an NIH NA-MIC Collaboration Grant EB005973.
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'''Figures:'''
 
 
'''Program Usage:'''
 
VoxelMeshingModule
 
 
  --imagefilename      Input image File Name
 
  --maskfilename      Input mask File Name
 
  --abaqusfilename    Output Abaqus Filename
 
  --vtkfilename        Output mesh VTK filename
 
  --vtksurfacefilename Output mesh surface VTK filename (Hack required for slicer3)
 
  --resamplesize      The image resample downsampling factor - Must be odd
 
  --meshindexoffset    The mesh index offset for nodes and elements
 
  --poissonratio      Poisson Ratio for the mesh
 
  --abaqustitle        Abaqus title for generated mesh
 
  --numberofbins      The number of histogram bins in the mesh
 
  --histogamlowerbound The lower bound for the mesh histogram
 
  --histogamupperbound The upper bound for the mesh histogram
 
  --histogambinfile    Mesh material properties histogram bin filename
 
  
'''Figures:'''
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[[Image:MappedHexMeshSquareSphereInit.jpg|left|thumb|300px|Initial position of the cube template mesh and the sphere surface prior to registration using the itk::FEM mapped meshing algorithm]]
  
[[Image:Slicer3Surface.png|left|thumb|300px|Surface of proximal phalanx generated via Slicer3]]
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[[Image:MappedMeshCubeSphereQuality.jpg|left|thumb|325px|Mesh quality evaluation of the warped cube]]
  
[[Image:VoxelMesh.png|left|thumb|300px|Voxel mesh generated via Slicer3 execution Model]]
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[[Image:MappedMeshSquareSphere.jpg|left|thumb|300px|a)Position of the template cube mesh and surface after ICP registration. b) Resulting warped cube after itk::FEM mapped meshing. c) Distance map between the warped cube and the sphere surface]]
  
[[Image:Mimx.png|left|thumb|300px|Slicer3 Voxel Mesh Module]]
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[[Image:MappedMeshProximalPhalanxTrial.jpg|left|thumb|300px|Initial attempt to apply mapped meshing algorithm to the proximal phalanx]]

Latest revision as of 18:27, 10 July 2017

Home < Mapped Hexahedral Meshing

Objective:

  • Develop a tool for mapped meshing that will warp a template mesh onto a surface for a new subject
  • Determine the limits that the warping algorithm will succeed and fail
  • Apply these techniques to a sample of data to determine the reliability of the algorithm with respect to mesh quality

Progress:

  • Previous work on this project was performed at the 2007 AHM - Mapped Mesh 4 Block
  • Warped meshing framework has been developed using VTK and ITK using a finite element approach
    • VTK
      • Support the reading and writing of meshes (vtkUnstructuredGrid) and surfaces (vtkPolyData)
      • Distance measures between the deforming mesh and the subject surface
      • Initial registration - Iterative Closest Point or Procrustes
    • ITK
      • Finite element framework used to warped the template mesh onto the subject surface
  • Registration made hierarchical to speed up the registration process
    • Requires multiple template meshes to exist
    • This is readily supported using the interactive meshing tools by changing the average edge length
    • Subsequent meshes are initialized using a thin plate splines
  • Parameters allowed to vary at each level of the registration
    • Iterations
    • Young's Modulus
  • Convergence based on distance between the warped template and the subject surface
    • User specified convergence threshold in mm
    • Convergence can be based on average or maximum distance
  • Boundary conditions can be applied
    • Center of the mesh - Holds the eight nodes closest to the center of the mesh fixed
    • External - Applies boundary conditions to the mesh as they fall within a user specified tolerance of the subject surface
  • Initial testing done by warping a cube mesh onto a sphere
    • Evaluation:
      • Distance between warped mesh and subject surface
      • Mesh quality

Publications:

Key Investigators:

  • Iowa: Nicole Grosland, Vincent Magnotta, Ritesh Bafna

Links:


Figures:

Initial position of the cube template mesh and the sphere surface prior to registration using the itk::FEM mapped meshing algorithm
Mesh quality evaluation of the warped cube
a)Position of the template cube mesh and surface after ICP registration. b) Resulting warped cube after itk::FEM mapped meshing. c) Distance map between the warped cube and the sphere surface
Initial attempt to apply mapped meshing algorithm to the proximal phalanx