Biomedical Engineering Reference
In-Depth Information
Fig. 5.26 Generation of an axissymmetric model based on one MR-slide: a FE-model, and
b comparison between axissymmetric and full 3D-model and experimental data
Table 5.6
in vivo fat and muscle parameter sets derived from axissymmetric modelling
Dj (M
-1
Pa
-1
)
j
l
j
(MPa)
a
j
(-)
Gluteal skin/fat
1
4,961E-04
-0.9604
4,045E+01
2
8,690E-11
41.26
7,362E-01
Gluteal (passive) muscle
1,025E-03
-4,227E+00
1,958E+01
3,077E-07
-4,540E-01
4,828E+02
Model Verification: Verification of the simulated and measured quantities has
been shown in Fig.
5.24
c. In addition, visual comparison of the deformed tissue
shape of the simulation plot at maximum indenter displacement, Fig.
5.25
b, with
the corresponding MR-slice image is shown in Fig.
5.25
a. It is depicted in
Fig.
5.25
c as a superposition of the simulation result on the MR-image (for clarity
only simulated outer skin/fat and muscle and bone tissue contours are shown).
Simplified Procedure for Material Characterization: Using the example of the
male volunteer M1 (cf. Table
5.2
), a simplified approach is presented to evaluate
tissue material parameters. This approach is applicable under certain anatomical and
experimental circumstances, provides similar results and is less elaborate and time
consuming. The experimental part involving force-displacement data generation, as
previously described, remains unchanged. The MR-image generation, however, is
strongly reduced and, in the simulation part, instead of a full three-dimensional finite
element model an axissymmetric model is employed. The reduced axissymmetric
model relies on a single (transversal) MR-image only where the axis of rotation is the
indenter axis, cf. Fig.
5.26
a. Comparing the results obtained from the full three-
dimensional model and the experimental results shows good agreement, Fig.
5.26
b.
One major requirement for this simplified approach is that the location of the
indentation test point is oriented such that the MR-image information is mirror
