Biomedical Engineering Reference
In-Depth Information
Fig. 6.15.
Deformation states of artery and balloon during multi-step cerebral angioplasty simula-
tion. State A: arterial physiological state before angioplasty (transmural pressure Δ
p
=
13
.
33
KPa
and axial stretch λ
Z
=
1
.
1); State B: initial contact of balloon and artery after balloon deploys; State
C: maximum balloon inflation with arterial dilatation to 130 % of the internal diameter; State D:
arterial physiological state after angioplasty displaying residual deformation in parts of the vessel
Results
The distributions of arterial tissue damage in the IEL and media layers are shown
in Figs. 6.16 and 6.17 for two different balloon inflation levels during PTA: 120 %
oversized dilatation state (an intermediate state between States B and C), and 130 %
oversized dilatation state (State C in Fig. 6.15). The maximum arterial damage can
be seen at the outer region of the balloon-artery contact. As the deformation is in-
creased from 120 % to 130 %, the damage variable increases in magnitude and the
damaged region extends further outside the balloon contact area. At 120 % dilatation
the maximum elastin damage in the IEL is
d
0
E
=
.
0
27, the maximum ground ma-
trix damage in the media is
d
0
M
=
0
.
22, and the maximum collagen damage in the
media is
d
iM
=
17. For further dilatation to 130 % (maximum balloon inflation),
arterial damage further accumulates to the following maximum values:
d
0
E
=
0
.
0
.
71,
d
0
M
=
27.
Fig. 6.18 shows the distributions of the von Mises stresses in the IEL, me-
dia and adventitia layers at the 120 % oversized dilation level. The largest arterial
stresses are found in regions corresponding to the highest IEL and media damage
shown previously in Fig. 6.16. Compressive radial Cauchy stresses are also seen
in highly damaged regions of the IEL and media (not shown). Fig. 6.19 similarly
shows the distribution of von Mises stresses in the IEL, media and adventitia lay-
ers after the completion of angioplasty (State D). The maximum stress values after
unloading have shifted to regions where residual deformation remains. The min-
imum von-Mises stresses is seen in highly damaged regions of the IEL after un-
loading.
0
.
49 and
d
iM
=
0
.
