ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

organ’s tissue anisotropy, and b) its outer geometry and inner material distribution.
Furthermore, many researchers confirmed local orthotropic anisotropy by experimental
evidence [4].
Based on anatomical knowledge, we reduce the organ to some characteristic inner
skeleton reflecting its inner structure [5]. Referring to the organ’s outer shape we
expand this inner skeleton to some “skeletal fiber field” covering the whole organ.
Thereafter, the organ’s surface normals are used for construction of the “radial” (e.g. in
the case of long bones) trajectories. A cross product of the skeletal fibers and the radial
trajectories produces the circumferential trajectories. Finally, the cross product of the
radial and the circumferential trajectories delivers the axial trajectories [6].
Exemplarily, we start from a tetrahedral
finite element grid of a fully dentate
mandible consisting of 14998 tetrahedrons
(Fig. 1). The respective surface file in stlformat
comprises 2516 points and 5028
triangles. In Step 1, the skeletal fiber field
which is already similar to the axial to the
axial trajectories is deduced from the
polygonal surface file, the inner skeleton,
and a point cloud covering the 3D-volume
of the mandible (Fig. 2). With regard to
the orthotropic anisotropy of the mandibular
bone, the radial trajectories are constructed
(Fig. 3). As described above, the
Figure 1. Tetrahedral finite element grid
of a fully dentate mandible.
circumferential and axial trajectories are calculated (Figs. 4 and 5).
Figure 2. Calculation of the skeletal fiber field (Step 1 of the procedure).