The generation of each anatomical model includes the following 7 steps: 1) recruitment and whole-body scanning of a volunteer, 2) pre-processing of the MRI data, 3) segmentation of the image to generate a label-field, 4) processing of the label-field to remove artifacts, 5) extraction of the tissue surfaces, 6) processing of the surfaces, and 7) quality control. Detailed information is availabe in Gosselin et al. 2014.
Imaging and image pre-processing
Segmentation and label-field processing
Surface extraction and processing
Model processing consists of: 1) discretization, i.e., transformation of models into voxels, tetrahedra, etc., for numerical modelling, 2) posing, i.e., posture parameterization, 3) morphing, i.e., changes in a model's morphology, and 4) material assignment. Model posing and morphing are important tools used to extend the population coverage without generating models de novo. Detailed information is availabe in Gosselin et al. 2014.
With the collaboration of SPEAG, users of Sim4Life and Semcad X can now use the Virtual Population as posable models, i.e., model postures can be changed to represent realistic exposure scenarios.
The morphing functionality allows, e.g., the fat or muscle content to be increased or decreased to change the body-mass index (BMI) of a model while preserving realistic internal organ placement and tissue distribution.
Tissue parameters can be assigned for various physics, e.g., electric and magnetic conductivity, permittivity, and permeability for EM simulations, or thermal conductivity, heat generation rate, heat transfer rate (perfusion), and heat capacity for thermal simulations. Material assignment is based on our database of tissue properties.
Virtual Population V2.0 - supplementary information
The V2.0 surfaces are generated from image segmentations using a technique, which is guaranteed to produce surfaces with compatible interfaces between tissues (triangles are shared between neighboring tissues) and have no self-intersections. These two criteria, as well as good approximation to the segmented labelfields and acceptable triangle element quality have been achieved through dedicated mesh processing algorithms. Please note that compatible surfaces guarantee there are no gaps or overlaps between tissues.
Naturally, since the surfaces are compatible at tissue interfaces, the complete surface (of all tissues) is non-manifold where more than one tissue meets at an edge. Please note, that we cannot guarantee that individual tissue surfaces are manifold.
What does this mean?