Biomedical Engineering Reference
In-Depth Information
ideas are introduced. Avoiding the occurrence of plastic strain is necessary. Further-
more, stresses within the scaffold should be as low as possible, because stresses can
accelerate magnesium corrosion [
26
]. The intention of this research is to propose an
improved scaffold design with the potential for extended durability. This design will
need to be verified through in vitro and in vivo tests.
2 Simulation of Flat and Preformed Scaffolds
2.1 Finite Element Modeling
2.1.1 Heart Movement
A heart attack can occur in different regions of the myocardium. In this feasibility
study, we focused on the anterior basal area because of its almost planar surface
topography. Based on values of magnetic resonance imaging (MRI) of 28 patients,
the average heart curvature was measured in two different planes; averaged values
are given in Table
1
. Formulas of circular segments were used to define the following
displacements:
r
sa
sin
x
r
sa
x
=
−
x
(1)
r
v
a
sin
y
r
y
=
−
y
(2)
v
a
r
sa
cos
x
r
sa
1
r
va
cos
y
r
va
1
z
=
−
+
−
.
(3)
With these, a circular plate can be deformed into a double curved shape as shown in
Fig.
1
. This represents a simplifiedmodel of a myocardium, whereby heart movement
is simulated through changes between the radii of end diastolic and end systolic state.
Ta b l e 1
Averaged anterior basal heart curvature [
25
]
Heart radii
Vertical long axis
(
r
va
)
(mm)
Short axis plane
(
r
sa
)
(mm)
End diastolic
49.7
25.1
End systolic
45.7
21.3
Mean value (preformed)
47.7
23.2
