Biomedical Engineering Reference
In-Depth Information
2.3 In Vivo Experiments with Human Tissue
Data acquisition for in vivo experiments on the human body requires a combination
of force-displacement testing. This can be achieved with tissue indentation together
with simultaneous tissue imaging, such as MRI or CT techniques, to capture the
undeformed anatomy at an initial unloaded state and the deformed anatomy under
loading. Based on the 2 D-imaging data of arbitrary undeformed tissue regions,
3 D-surface information of the anatomical structures can be reconstructed using
3 D-reconstruction tools. This surface data is used for FE-modeling. Compressive
indentation testing is most commonly employed in in vivo force-displacement
experiments, due to the high flexibility of fat, connective and muscle tissue. The main
challenge was to develop an appropriate experimental design (MRI or CT compatible
testing device) and an evaluation procedure to separate the material behavior of the
single tissue components, based on the experimental results gained from the tissue
compound material. The methods for material parameter determination as well as
evaluation of the viscoelastic material properties of biological tissue employ the
same procedure (inverse FEM), cf.
Sects. 3.4
and
5.2
.
2.4 Ex Vivo Experiments with Human Tissue
Acquiring in vivo data from mechanical experiments on human ligaments, tendons
or blood vessel wall material is not feasible to date. Thus, samples such as
aneurysm wall material have been removed from patients during surgery or taken
post mortem and then subjected to mechanical characterization. Uniaxial or
multiaxial tensile tests are most often performed. The method is based on the
experimental results and employed for material parameter identification and is
orientated according to the in
Sects. 5.2.2
-
5.2.5
representated procedure.
2.5 Design Data (CAD Data of Technical Support Devices)
Design data of the tSD is used as the basis for finite element mesh generation.
If such data is not available, it must be manually generated.
2.6 FE B
OSS
-Models
To simulate the interaction between the human body and a tSD, adequate models
of the human body and single body regions, including realistic anatomy as well as
in vivo tissue material properties are indispensable. Magnetic resonance imaging
