Biomedical Engineering Reference
In-Depth Information
Table 7.4
Comparison of stenosis for ICA and ECA with respect to CCA. Carotid bifurcations of
patients (1/L), (1/R), (5/L) and (6) are severely stenosed at the location of their ICA. At the ECA,
patients (4/L) and (5/R) have the most serious clogs. Note that a higher degree of stenotic severity
is indicated by a lower ICA/CCA
or ECA/CCA ratio (%)
Comparison of carotid bifurcation stenosis
Patients
(1/L)
(1/R)
(2/L)
(2/R)
(3)
(4/L)
(4/R)
(5/L)
(5/R)
(6)
CCA (mm
2
)
32.1
30.3
20.2
24.5
28.7
41.0
24.1
27.3
31.6
34.6
ICA (mm
2
)
2.9
3.0
9.8
12.1
12.7
13.5
8.0
8.7
7.2
8.8
ICA to CCA
ratio (%)
9
10
49
49
44
33
33
32
23
25
ECA (mm
2
)
17.8
11.7
4.7
6.8
11.2
9.3
8.0
7.1
3.8
14.0
ECA to CCA
ratio (%)
55
39
23
28
39
23
33
26
12
40
severe blockage (up to 70 % occlusion). Blood vessel on (2/L) and (2/R) are slightly
stenosed (approximately 40 % occlusion).
The ICA and ECA angles with respect to the CCA are described in Table
7.3
.
Note that the angle between ICA and CCA varies from 10 to 65°. The angles 57°
(case (4/L) and 65° (case (4/R) are notably higher than the rest of angles for the
other patients. The angle between ECA and CCA ranges from 0 to 35°. The case
subjects (1/R) and (6) have angles 33 and 35° that are comparatively higher than the
angles pertaining to the other patients.
Detailed comparison for ICA and ECA stenoses based on the ten case studies
from the six patients are given in Table
7.4
. Patients (1/L), (1/R), (5/R) and (6) have
severe stenosis at the ICA, with ICA to CCA ratios of 9, 10, 23 and 25 % respec-
tively, and patients (4/L) and (5/R) are heavily stenosed at the ECA with ratios of 23
and 12 % respectively. Although not displayed in the table, it may be worth noting
that the CCA of patient (4/L) has an area reduced to 5.0 mm
2
at its bifurcation. Also,
the CCA area for patient (5/R) is reduced until 14 mm
2
at bifurcation.
The geometry of subject (3) was taken from a healthy carotid bifurcation with
no signs of stenosis. The CCA, ICA and ECA diameters of the measured sample are
6.00, 3.98 and 3.96 mm respectively, while the diameters of the standard anatomy
are 6.2 (at CCA), 4.4 (at ICA) and 3.5 mm (at ECA). The angle between the ICA
and ECA is approximately 40°, which is a small deviation compared with the stan-
dard geometry at 50°.
7.3.3
Comparison of Wall Shear Stress Computational Models
7.3.3.1
Wall Shear Stress Contours at Peak Systole
It has been indicated by previous studies that wall shear stress promotes luminal
thinning and plaque rupture (Berger and Jou 2000; Gertz et al. 1981; Zohdi 2005)
and low WSS regions are more prone to athersclerosis (Plank et al. 2007). The
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