Biomedical Engineering Reference
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particle image velocimetry (DPIV) system was used to measure the pulsatile
velocity and shear stress fields within the aneurysm. Their results showed that
peak velocity and strength of vortices inside the aneurysm sac were reduced
after placing the stents. Same authors [25] conducted an experimental study
to measure the changes in the intraaneurysmal fluid pressure and parent vessel
flow characteristics resulting from packing the aneurysmal sac with hydrogel-
coated coils. Their results showed that the intraaneurysmal fluid pressure did
not increase when packing the aneurysm with hydrogel-coated platinum coils,
even with a coil density up to 93%. Gobin et al. [26] observed reduction of
inflow and flow stagnation at the dome with coil insertion in their in vitro
model study.
There are numerous reports of clinical experience with placement of stents
and coils in brain aneurysms (see, e.g., Marks et al. [27], Wakhloo et al.
[16]). Lanzino et al. [28] reported that stent placement within the parent
artery across the aneurysm reduced intraaneurysm flow velocity, which led
to intraaneurysm stasis and thrombosis and consequently preventing rupture.
Kwon et al. [29] used a new endovascular technique for treatment of cere-
bral aneurysms. Eight patients with wide-necked aneurysms were successfully
treated without complications with detachable coils using the multiple micro-
catheter technique. Meckel et al. [30] conducted an in vivo study to quantify
flow velocities and to estimate WSS in patients with cerebral aneurysms using
magnetic resonance imaging (MRI). Their results showed a high spatial vari-
ation of WSS among different aneurysm geometries reflecting variable flow
patterns.
6.4.2 Computational Studies Associated with Combined
Use of Stents and Coils for the Treatment of
Cerebral Aneurysms
Advanced modeling techniques have enabled multiphysics computations to
investigate hemodynamic and other factors contributing to disease progres-
sion. In addition, the combination of noninvasive diagnostic tools (e.g., MRI,
computed tomography [CT], or ultrasound) and computational fluid dynam-
ics (CFD) techniques provides key hemodynamics feedback for studies of
vascular diseases and to plan for therapeutic options [31-41]. Many stud-
ies have been conducted in the literature using idealized numerical mod-
els to study the flow patterns inside the aneurysms caused by the presence
of stents. For example, Aenis et al. [42] used finite element method, pul-
satile, Newtonian flows to study the effect of stent placement on a rigid side-
wall aneurysm. Their results showed diminished flow and pressure inside the
stented aneurysm. Ohta et al. [43] analyzed hemodynamic changes in intracra-
nial aneurysms after stent placement using a finite element modeling approach.
Their work illustrated areas with stagnant flow and low-shear rates after stent
placement.
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