Biomedical Engineering Reference
In-Depth Information
Fig. 5 Blood pressure distribution at 4 instants (T1, T2, T3, T4
0.2 s, 0.5 s, 0.7 s and 0.95 s,
respectively) over a cardiac cycle: note that blood pressure decreases along the tree, from the aorta
to the peripheral terminals. The highest pressure is about 15.5 kPa (116 mmHg) occurring at the
ascending aorta in systole
¼
appreciated from Fig.
5
that the blood pressure decreases from the ascending aorta
(inlet) to peripheral terminals (outlets). The highest blood pressure, 15.5 kPa or
116 mmHg, occurs at aorta in systole (0.2 s).
Since the blood pressure and flow velocity are solved at every time step of a
cardiac cycle, we can analyze the flow history at random points in the tree. This
feature is very useful because the exact location where a vessel lesion is found can
be located in the tree, and haemodynamic analysis at that site can be performed. For
instance, the pressure and flow velocity waveforms for cerebral arteries, e.g., the
common carotid artery (CCA), internal carotid artery (ICA), middle cerebral artery
(MCA), anterior cerebral artery (ACA), and vertebral artery (VA) are plotted in
Fig.
6
. We observe that the pressure waveforms are similar in their temporal
profiles, and that the pressure drop is small in large arteries. This is consistent
with the physiological nature of the cardiovascular system. The flow rate (
F ¼ VA
),
however, must satisfy the conservation law of mass. This is realized via the
enforcement of (
1
) and the bifurcation model, e.g.,
F
CCA
¼ F
ICA
þ F
ECA
.
Validation of the velocity waveform for the CCA was performed using duplex
Doppler ultrasonography, and was reported in our previous work [
6
]. The validation
results revealed that the magnitude (
300 mm/s) and temporal profile of our model
conformed with the ultrasonic measurement. Validation for other intracranial
arteries are yet to be performed via transcranial Doppler sonography.
