Human Body Models: BOSS-Models - Preventive Biomechanics - page 214

Fig. 5.36 Steps in the generation process of complete human models, a MRI slices of the human
gluteus, b 3D-reconstruction, c FE-model, and d work flow chart from MR-imaging to finite
element analysis
accordingly. This is mainly done by manually reconstructing (identifying) the
single tissue types, e.g. skin, fat, muscle, bone etc. of each image slice. Figure 5.35
demonstrates the general reconstruction procedure using the example of pelvic
bone and hip joint identification. Using three-dimensional reconstruction tools, e.g.
M IMICS , the structures are graphically marked and after completion, the marked
information of all slices is combined to generate a three-dimensional surface.
By means of a pre-processing tool, such as H YPER M ESH , the reconstructed
surfaces are imported and FE-meshed. The finite element mesh may represent the
anatomy of the complete body or body region at an initial unloaded (undeformed)
state, Fig. 5.36 a-c, as well as at any loaded (deformed) state. The single steps are
illustrated in Fig. 5.36 d.
A complete human model includes blood vessels, tendons, ligaments, nerves etc.
However, data acquisition from a complete human model using imaging techniques
would be technically difficult and entail formidable work. Also, acquiring (in vivo)
material properties would be difficult and simulating such detailed models would
consume enormous computational power. Thus, a more feasible approach is to
concentrate on the anatomical region relevant to a particular loading scenario and
to model this region as accurately as possible. Such a region might be a section of a
blood vessel to investigate interaction with a stent (cf. Fig. 4.1d ). Or it might be to
model skeletal motion, including soft tissue regions, or to investigate the human
foot interacting with a shoe (cf. Fig 4.1b ). However, when restricting an investi-
gation to a human body part, the application of finite element modelling requires
intuition and experience to compensate for the mechanical influence of neglected
body regions and to maintain physical correctness.