computational design of intracranial stent using 3d ... · (population survey report ) minimal...
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Computational design of Intracranial Stent p gusing 3D visualization system
Institute of Fluid Science, Tohoku UniversityMakoto OHTA
Graduate school of EngineeringHitomi Anzai
Graduate school of Biomedical EngineeringToshio Nakayama
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Background
Cause-specific death rate in Japan (H19) Endovascular treatment
Causes of death Stent placement
(Population Survey Report )
Minimal invasivenessGood prognosis of pationts
Endovascular treatment
Malignantneoplasm35 8%P i
otherSole stenting
Reduction of flow in aneurysm35.8%Pneumonia
11.7%M. Aenis et al. (1997)
aneurysm
Heart disease18.7%
Cerebral vasculardisease13.5%
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Cardiovascular disease32.3%
stent strut
Integration of realistic stent data to realistic patient data
Our team firstly succeeded to develop this method in the world
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y pAnd provided this techniques to VISC (2006).
MethodAne r sm and stent geometr as reconstr cted merging geometriesAneurysm and stent geometry was reconstructedusing Digital Subtraction Angiography and Micro CT
merging geometriesusing 3D CAD technique
Inlet
OutletInlet・Velocity : 0.162 [m/s]・Density : 1050 [kg/m3]
Numerical simulation・Finite Volume Method・Incompressible-Newtonian
Boundary condition on the wall・Non-Slip
Outlet
Density : 1050 [kg/m ]・Viscosity : 0.0035 [Pa・s]・Reynolds number : about 200
(assuming Basilar Artery)O
pfluid
・Equation of continuity・Navier-Stokes equations・Steady flow
Mesh・The number : about 1,200,000
(in all cases)T T h d
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Outlet・Pressure : 0 [Pa]
・Steady flow・Fluent 6.3 (Fluent, Inc.)
・Type : Tetrahedron・Using Size Function
Figure: Stent image
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Silk stent
Still tStill rupture...Risk of embolizationStill underfinished..Less materials is better
We need to reduce the material volume
Look for the most effective (reduce-able) point
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Realization Workspace (CAVE) in IFS3D realization may help a lot for understanding the flow3D realization may help a lot for understanding the flow
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Specification of inflow zone
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Purpose
Background and Purpose
To verify the validity of 3D visualization to understand the flowon stent as a new way of stent development
Purpose
Flowchart
G d t t ?
Numerical Simulation
Good stent ?Good knowledge about
effective stenting ?
3D Visualization
Discussions
Improvement of stent
Numerical simulation
Specification of inflow zonecc
Numerical simulation(before strut addition)
& Inflow zone
Inflow from Inlet
3D visualization
Addition of strutto cover inflow zone
Outflow to Outlet
Flow
“Inflow zone”Add a strut at this position
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Addition of strut
• Strut diameter : 0.15 [mm]
• Curvature : 667 [1/m]
• Change strut position
x=0.50[mm] x=1.30[mm] x=2.00[mm]12
The role of stent strut on the flow
FlowAddition of strut
x=1.00[mm]x=0.50[mm] x=1.30[mm]Velocity
SSWSS
x=1.65 [mm] x=2.00[mm]15
The most effective stenting position ・・・?
Flow is very complex around aneurysm!We cannot understand what factor can reduce the flow without visual information!
To verify the validity of 3D visualization to understand the flowPurpose
We cannot understand what factor can reduce the flow without visual information!
To verify the validity of 3D visualization to understand the flowon stent as a new way of stent development
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Models We used 3types of real arterial geometry
MethodModels
Flowchart
We used 3types of real arterial geometry
Numerical Simulation
3D VisualizationConditions
Inlet・uniform velocity profile
Outlet・Pressure: 0 [Pa]
Discussions
・uniform velocity profile ・steady flow・rate: 2.36×10-6 [m3/s]
・Pressure: 0 [Pa]Viscosity: 4.0×10-3 [Pa⊕s]Density: 1.0×103 [kg/m3]
Improvement of stent
3D visualization
We visualized numerical results in Realization
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Workspace (AFI-IFS)Software : EnSight Gold 8.2 (CEI)
Results1 Specification of inflow zone
2 inlets & 1 outlet 1 inlet & 3 outlets1 inlet & 1 outlet
Inflow zone Inflow zoneInflow zone
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Proceedings of ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting and 8th International Conference on Nanochannels, Microchannels, and Minichannels FEDSM2010-ICNMM2010 August 1-5, 2010, Montreal, Canada
FEDSM-ICNMM2010-30591THE EFFECT OF 3D VISUALIZATION ON OPTIMAL DESIGN FOR STRUT POSITION OF INTRACRANIAL STENT
Hitomi Anzai, Toshio Nakayama, Yuriko Takeshima, Makoto Ohta
Results2 Strut placement1 inlet & 1 outletStrut position 1 inlet & 1 outlet
■Strut position was decided to disturb inflow from parent artery
Strut position
from parent artery.■Strut was placed using 3D CAD techniques.
Strut
Without strut With one strut2 inlet s& 1 outlet
After placement Strut
■The flow direction is changed.■WSS di trib ti i
p
Strut
1 inlet & 3 outlets■WSS distribution is changed.
18Without strut With one strut
Parameter Study of HemodynamicsParameter Study of Hemodynamics Simulation at Internal
Carotid StenosisCarotid Stenosis
○ Toshio Nakayama Institute of Fluid Science, Tohoku University
Hitoshi Hayase Neurological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, y
Koji Tokunaga Neurological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
Makoto Ohta Institute of Fluid Science, Tohoku UniversityMakoto Ohta Institute of Fluid Science, Tohoku University
Nakayama, Hayase, Tokunaga, Ohta, J. Flu. Sci. Tech. 3, 544, 08The effect of outlet pressure on the flow distribution
0P 280P 420P0Pa 280Pa 420Pa
Simulation ResultsSimulation Results
• Flow rate proportion & maximum flow• Flow rate proportion & maximum flow velocity of ICA ECA
Pressure to internal carotid artery [Pa]
0 70 140 210 280 350 420
Max.Velocity (ICA) [m/s] 1.3200 1.2903 1.2608 1.2324 1.2017 1.1723 1.1867
Max.Velocity(ECA) [m/s] 1.0532 1.0770 1.1000 1.1220 1.1467 1.1701 1.1932
Flow rate proportion 1.2533 1.1980 1.1461 1.0983 1.0479 1.0018 0.9945
• Output of ultrasound – ICA: 1 124[m/s] ECA: 1 094 [m/s]ICA: 1.124[m/s], ECA: 1.094 [m/s]– Flow rate proportion: 102.74
The proper flow rateThe proper flow rate
•• The proper of flow rate:Flow rate of simulation
= Flow rate of ultrasound
I t ti i t liporti
on
Intersection in two lines
Form figure,I t l tid t 310 922[P ]at
e to
pro
•Internal carotid artery: 310.922[Pa]
Flow
ra
[Pa]Pressure:Flow rate of ultrasound
:Flow rate of simulation
ResultsResults
• The Proper Case ResultsThe Proper Case Results• Outlet Condition
– ICA:310.922 [Pa]ICA:310.922 [Pa]– ECA:0 [Pa]
• Velocity (Measurement Position))– Internal carotid artery:
1.1888[m/s]– External carotid artery:
1.1585[m/s]
Optimisation of StentsOptimisation of Stents
Makoto OHTA, K SrinivasInstitute of Flow Science, Tohoku Universityy
Sydney University
OptimisationOptimisationOptimisationOptimisation
Latin HypercubeLatin Hypercubesample Variables
FLUENTE l t FitEvaluate Fitness
KriggingThe best candidate
60 samples
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Two-dimensional optimisation of a stent for cerebral aneurysm
K. Srinivas, M. Ohta, T. Nakayama, S. Obayashi, T. Yamaguchi
Journal of Medical Devices (accepted)
Objective FunctionObjective FunctionObjective FunctionObjective Function
MaximiseMaximiseMaximise Maximise Velocity
Reduction Shear StressReduction in
C iinCavity
Cavity
VorticityyReduction in
Cavity
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Computational DetailsComputational Details5mm
5mm
5mm
10mm4mm
40mm
10mm
• 2D Computation with 75,000 nodes• Reynolds Number 300 Inlet velocity 0 3 m/sReynolds Number 300, Inlet velocity 0.3 m/s. • Standard Boundary Conditions• Each calculation about 2 mins on Super ComputerEach calculation about 2 mins on Super Computer
Non Dominated SolutionsNon Dominated Solutions(Aneurysm)(Aneurysm)
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Optimal StrutOptimal Strut--Gap ArrangementsGap ArrangementsOptimal StrutOptimal Strut Gap ArrangementsGap Arrangements
⊗ V -max
-max⊗
V ma⊗
compromise
V -max⊗
-max⊗
compromise
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Proceedings of ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting and 8th International Conference on Nanochannels Microchannels and Minichannels
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International Conference on Nanochannels, Microchannels, and Minichannels
FEDSM2010-ICNMM2010 August 2-4, 2010, Montreal, Canada FEDSM-ICNMM2010-30592
DEVELOPMENT OF STENT STRUT PATTERN FOR CEREBRAL ANEURYSM
Toshio Nakayama, Shinkyu Jeong, Srinivas karkenahalli, Makoto Ohta
Conclusion
・WSS distribution and flow pattern were changed by one strut.・3D visualization system may be useful to observe flow pattern around strut.・These 3D information may be helpful to design stent strut pattern.
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Thank you for your attention
www.ics-meeting.net
AcknowledgementAcknowledgement
Global COE in IFS, Tohoku University, JSPSCore to core in IFS, Tohoku University, JSPSG t i id JNIHGrant-in-aid, JNIHGrant-in-aid, JSPS
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