affected zone for cerebral aneurysm AACherevko APChupakhin ALKrivoshapkin AKKhe KYOrlov PASeleznev Lavrentyev Institute of Hydrodynamics SB RAS Meshalkin ID: 577661
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Slide1
Numerical modelling of affected zone for cerebral aneurysm
A.A.Cherevko, A.P.Chupakhin, A.L.Krivoshapkin, A.K.Khe, K.Y.Orlov, P.A.Seleznev
Lavrentyev Institute of Hydrodynamics SB RASMeshalkin Novosibirsk Scientific Research Institute of Circulation Pathology
6th Russian workshop on mathematical models and numerical methods in biomathematicsSlide2
Outline
Purposes and stages of workMedical information 3D-reconstruction of the cerebral vascular systemHemodynamic modelingAssessment of the region of influence of the aneurysm on hydrodynamic characteristicsDetermination of influence on the aneurysm high blood pressure ( Hypertension) and low blood pressure (Hypotension)Slide3
Stages of work
3D- geometric reconstruction of circulation of the cerebral vascular system with and without aneurysm based on tomograms (data from Meshalkin Novosibirsk Scientific Research Institute of Circulation Pathology) Hemodynamic modeling based on the software package ANSYS-CFX using the 3D- geometric reconstruction
Assessment of the region of influence of the aneurysm on hydrodynamic characteristics.
Determination of
pressure’s influence
on the aneurysm
(high blood pressure and low blood pressure)
PurposesSlide4
An
aneurysm is a weak area in the wall of a blood vessel that causes the blood vessel to bulge or balloon out.
Locations of aneurysm’s appearance
:arterial bifurcations, space of anatomical changes of
vessel
’
s
structure
, arteriovenous malformations. The major factors
: structural changes in the arteries, hemodynamic
s,
wall biomechanics
.
A person may have an aneurysm without having any symptomsSymptoms : double vision,loss of vision,headaches,eye pain,neck pain,stiff neckRepair an aneurysm: Clipping and endovascular repair is most often done. It usually involves a "coil" or coiling, this is a less invasive way to treat some aneurysms.Slide5
Benchmark data
– Computed tomography (CT) and magnetic resonance imaging (MRI) scans of the brainThickness- 0.8
mm, amount of scans-150 for each model
Reconstruction of two models of the cerebral vascular system with aneurysm on
Middle cerebral artery
(
model
А
)
Anterior communicating artery’s bifurcation(
model
В
).
Size of each aneurysm is about 4 mm.3D-reconstructionSlide6
Seg3D и ITK-SNAP
RESAMPLE tool to change and improve the resolution of the tomograms in SEG 3D programITK-Snap program
to build 3D-geometry of the cerebral vascular system with aneurysmsSlide7
ITK-SNAP
The methodology behind SNAP is called snake evolution. The term snake is used to refer to a closed curve (or surface in 3D) that represents a segmentation. In snake evolution methods, the snake evolves from a very rough estimate of the anatomical structure of interest to a very close approximation of the structure, as illustrated in the figure belowУравнение построения фронта(змеи):
,whereα –propagation coefficientβ – curvature coefficient
к - curvature
- luminance
- velocity of spreadingSlide8
Reconstructed 3D-Model before smoothing
Specific layered features. Possibly presence of artifacts – excess parts which are not vessels and also splicing of vesselsSlide9
Final 3D-Model with aneurysm
Model AAneurysm on theMiddle cerebral
artery
Model BAneurysm on the
Anterior
communicating artery’s
bifurcationSlide10
Final 3D-Model without aneurysm
Model AWithout Aneurysm on theMiddle cerebralartery
Model BWithout Aneurysm on the Anterior communicating artery’s bifurcationSlide11
The main stage of work
- hydrodynamic calculation - ANSYS CFX software which consists of six components that take a geometry and mesh and pass the information required to perform a hydrodynamic analysisHemodynamic modeling. ANSYS-CFXSlide12
The mesh consists of
tetrahedrons. The mesh is automatically refined based on geometry curvature. This willresult in larger elements on flat planar surfaces and smaller elements in areas of high curvature.Model A: quantity of nodes- 195226, quantity of elements– 1019089.
Model B: quantity of nodes - 208691, quantity of elements - 1070303.
Mesh generation
with
aneurysm
CFX — Mesh
ing
(ANSYS ICEM CFD)
A
BSlide13
Mesh generation without
aneurysm CFX — Meshing (ANSYS ICEM CFD)Model A : quantity of nodes - 18754 , quantity of elements - 990567Model B
: quantity of nodes -196536, quantity of elements-1006249,
BSlide14
Mathematical Statement of the Problem
Blood flow described by the Navier-Stokes equations for three-dimensional motion of an incompressible, viscous Newtonian fluid where v - velocity, p - pressure, ν - the kinematic viscosity, Ω - the internal volume of the computational domain, including the configuration of the vessels in the form of the tee and the aneurysm. γ = ∂ Ω - boundary wall of the vessel. Boundary conditions: Where and - velocity and pressure
-Slide15
Computational area. Steady State
ANSYS CFX — Pre. Model А Diameter of the biggest
vessel is 5 mm (Input), Diameter of the smallest -
1,02 mm (Output2)
Boundary Conditions
:
V
=100
cm/s
on
Input
,
P=40 mmHg on Output(3,5), P=35 mmHg on Output4, P=30 mmHg on
Output(1,2).Slide16
Computational area. Steady State
ANSYS CFX — Pre. Model В Diameter of the biggest vessel is 4,87 mm (InputRight), Diameter of the smallest
- 0,412 mm (OutputRight2).
Boundary Conditions:
v=100
cm/s
on InputLeft,
InputRight, P=40mmHg on OutputLeft1, OutputRight1
,
P=35mmHg on
OutputLeft
(2,31,31),
OutputRight(2,3), P=30mmHg on OutputLeft4, OutputRight4Slide17
Assessment of the area of influence
of the aneurysm on hydrodynamic characteristicsSlide18
Comparative analysis
Allocation of pressure for Model A
Variations in the pressure are not observed(1,19% with respect to maximum value).Point of max value
moves on 2,6 mm, min
–
2.
8
mmSlide19
Comparative analysis
Allocation of pressure for Model B
Variations ~2%, point of max value moves on 3 mm
, min – 2.4 mmSlide20
Comparative analysis
Allocation of velocity for Model A
Variations - 20 cm/s (6% with respect to maximum value) in the region of the location of the aneurysm.
Point of max value moves on 4.6 mm, min – 1.4
mmSlide21
Variations in velocity is small (4% with respect to maximum value), point of max value moves on
5.1 mm, point of min value remains at the same location
Comparative analysis Allocation of
v
elocity
for
Model BSlide22
Comparative analysis
Allocation of wall shear stress (WSS) for Model A
Little changes (≈6%) about 0-0,2 mm Hg.Point of max value
moves on 5.2 mm, min – 4.6
mmSlide23
Changes are not observed, point of max value move on 5.7 mm, min
- 5 mm Comparative analysis Allocation of wall shear stress (
WSS) for Model BSlide24
∆max
Distance
(
mm
)
Pressure
mm Hg
1.2365
(1,19%)
2.6345
Velocity
cm/s
16.904
(5,5%)
4.6423
WSS
mm Hg
0.0
3
(0,96%)
5.2397
∆min
Distance
(
mm
)
Pressure
mm Hg
2.8991
(2,81%)
2.8523
Velocity
cm/s
2.68359
(0,88%)
1.4523
WSS
mm Hg
0.07
(2,25%)
4.6324
Model A
Changes for
max and
min values
in
the cerebral vascular system with and
without aneurysm
Distance
is length between points with max value (or min value) on the cerebral vascular system with and without aneurysmSlide25
∆max
Distance
(
mm
)
Pressure
mm Hg
1.5207
(1,83%)
2.9944
Velocity
cm/s
14.811
(4,61%)
5.1318
WSS
mm Hg
0.
05
(2,9%)
5.6795
∆min
Distance
(
mm
)
Pressure
mm Hg
0.9074
(1,09%)
2.493
Velocity
cm/s
6.48087
(1,99%)
0.7345
WSS
mm Hg
0.
0
2
(1,17%)
5.0148
Model B
Slide26
Pressure
Velocity
WSS
Distance is length between points with max value (or min value) on the cerebral vascular system with and without aneurysmSlide27
Summary points
Uniform pressure distribution for models with aneurysm;Velocity and pressure don’t change in the transition from the model with aneurysm to the model without aneurysm;Influence of the aneurysm on hydrodynamic characteristics is local;Aneurysm affects locally, in the future we can restrict by the area of influence of the aneurysm, which extends to 25 mm along the vessel on both sides of the aneurysm (outside the "zone of influence" of data changes are small).Slide28
Determination of influence on the aneurysm high blood pressure
(hypertension) and low blood pressure (hypotension)Slide29
Comparative analysis
Allocation of pressure for Model A. Modeling hypertension(increase of pressure on outlets on 30%) Pressure increases throughout model. Locally elevated pressure is not observedSlide30
Allocation of
pressure for Model B. Modeling hypertension(increase of pressure on outlets on 30%)Pressure increases throughout model. Locally elevated pressure is not observed
Comparative analysisSlide31
Allocation of
velocity for Model А. Modeling hypertension(increase of pressure on outlets on 30%)Flow reconstructs at a distance 4 cm (or 10 diameters of aneurysm)
Comparative analysisSlide32
Allocation of
velocity for Model B. Modeling hypertension(increase of pressure on outlets on 30%)Flow reconstructs at a distance 2 cm (or 5 diameters of aneurysm)
Comparative analysis
Changes of velocity close to the aneurysm are 5-10 cm/s between max values for each modelSlide33
Allocation of wall shear stress
(WSS) for Model А. Modeling hypertension( increase of pressure on outlets on 30%)
Comparative analysisChanges of WSS close to the aneurysm are not observedSlide34
Allocation of wall shear stress
(WSS) for Model B. Modeling hypertension( increase of pressure on outlets on 30%)
Comparative analysisPlace of locally elevated WSS
near the basis of aneurysm
Essential changes of WSS -0.2 mm Hg or 27 Pa (difference 30%)Slide35
Values of MAX and MIN of important hemodynamic parameters around the aneurysm for Model A
Values of basic parameters around theaneurysm Bench mark+30% for values of pressure on outlets
-30% for values of pressure on outletsMax WSS (mm Hg)
0,50,50,4
Min WSS
(mm Hg)
0,003
0,004
0,003
Max velocity
(cm/s)130
135
121
Max pressure
(
mm Hg)708057Min pressure (mm Hg)647552Slide36
Values of MAX and MIN of important hemodynamic parameters around the aneurysm for Model B
Values of basic parameters around theaneurysm Bench mark+30% for values of pressure on outlets
-30% for values of pressure on outletsMax WSS (mm Hg)1,050,98
0,9Min WSS (mm Hg)0,0018
0,0019
0,0016
Max velocity
(
cm/s)
146
155140Max pressure
(
mm Hg)
50,3
58
42Min pressure (mm Hg)35,54430Linear changesSlide37
Summary points
Little changes of max and min values of WSSWSS is locally elevated close to the aneurysm on the arterial bifurcationLinear changes of pressure on walls of vessel close to the aneurysm (4 mm) and also throughout modelLinear changes of max velocity values close to the aneurysmReconstruction of flow at the distance 4 cm (or 10 diameters of aneurysm) for model A and at the distance 2 cm (or 5 diameters of aneurysm) for model B
Modeling of high blood pressure(
Hypertension) and low blood pressure (Hypotension) has shown changes of basic hemodynamic parameters:
Make an assumption that aneurysm on arterial bifurcation could be
more danger
than aneurysm on the vessel’s wall.
During modeling of the brain’s vascular system can consider
local areas
close to the aneurysm (about 10 diameters of aneurysm)Slide38
Thank you for your attention!Slide39
ANSYS Geometry
Model A of the cerebral vascular system consists of two unconnected parts .It is an anatomical peculiarity of patient .The generate of mesh and the calculation have performed only for the component with aneurysm.