Transcript IGERT on CFD Louisiana State University

Glaucoma Simulation
& Visualization
Spring 2007 High School Workshop
Presenter
Farid Harhad. IGERT Associate. Computer Science
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT
Overview
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Motivation
What is Glaucoma?
Anatomy of the Eye
CFD Simulation of the Disease
Eye Simulation Data
Visualization of the Simulation
Tutorial Highlights
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Louisiana State University
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Motivation
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Investigating fundamental mechanisms of flow in
the eye helps us understand the leading causes of
glaucoma
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CFD simulation of glaucoma produces large
amounts of data that can only be interpreted and
analyzed using visualization
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT
Part 1:
Overview of the Disease
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What is Glaucoma?
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Glaucoma leads to blindness by damaging the
retinal cells[1]
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Elevated pressure in the eye is a risk factor, but
even people with normal pressure can lose vision[1]
World wide, second leading cause of blindness[1]
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Anatomy of the Eye (1/2)
[2]
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Light enters the eye by passing
through
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Cornea,
anterior chamber, pupil,
lens,
vitreous body,
retina
Optic nerve carries signal from
retina to brain
High fluid pressure damages
retinal nerve fibers and optic disc
begins to hallow
[3]
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Anatomy of the Eye (2/2)
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Ciliary body consists of ciliary muscle and ciliary
processes
Ciliary processes is a vascularized layer which
secretes a fluid called the aqueous humor (AH)
[2]
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Eye Fluid Drainage
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AH flows radially inward from ciliary body and drains in the
trabecular meshwork and Schlemm’s canals
CFD simulation done for angle-closure glaucoma
In angle-closure glaucoma, the iris deforms and blocks
normal flow
[5]
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[5]
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Eye Vascular System
[4]
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Part 2:
CFD Simulation of the
Disease
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CFD Simulation of Angle-Closure
Glaucoma
1.
Natural convection due to
temperature difference
between the ambient air (25 °C
/ 77 °F) and the interior of the
eye (37 °C / 98.6 °F) leads to
a buoyancy flow.
2.
Apply the conservation of
momentum law (fluid form of
Newton’s law) to model the
flow in the eye.
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[2]
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Buoyancy Effect in the Eye
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CFD Simulation of Glaucoma
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Mathematical equations of the physical model
are numerically solved w/ computers:
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Material particle method (deformable iris)
Immersed boundary (iris+fluid)
Fluid solver (fluid)
Eye geometry information
was modeled using
ANSYS software and fed
into the numerical model
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT
Part 3:
Visual Analysis of the
Simulation Results
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Eye Simulation Data
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Two types of datasets used:
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iris geometry: consists of the vertices of the tessellated
bottom surface of the iris
flow information: time-dependent velocities (u, v, w),
P, & T at 69741 locations in the eye.
IGERT on CFD
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Scalars
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Scalars
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Physical quantities that are completely characterized by
one number
Examples: mass of an object, temperature of an object,
electrical potential, height …
2844 lbs
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100 ºF
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1.5 V
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Vectors
30 ~ 60 μ Tesla
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[7]
Vector
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Consists of a magnitude and
direction
Vectors are often represented
graphically by arrows
Examples: velocity of an object,
gravity, magnetic field ...
Example:
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112 mph
[6]
IGERT on CFD
Louisiana State University
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Visualization Techniques
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Vector data: velocity distribution
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LIC (Line Integral Convolution) basic idea
[9]
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Visualization Techniques
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Scalar data: pressure distribution w/ colormaps
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Eg. often a color lookup table, is used to map a range of
scalar data to a predefined color
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Visualization Process
T=0,
T=1,
…
Eye geometry
render geometry
using polygons
Image
Sequence
(1574 timesteps)
T=1573
T=0,
T=1,
…
Vector data
render using LIC
Scalar data
render using a
colormap
T=1573
(1)
CFD
Simulation
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(2)
Data
Visualization
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(3)
Movie
Generation
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Visualization of The Results
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Recap
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Glaucoma is a group of diseases that leads to
blindness
Common cause is when the aqueous humor does
not drain properly and pressure buildup damages
the optic nerve
CFD computer model takes into account the
buoyancy flow and conservation of momentum
We visualize the velocity of the flow in the eye
using LIC (line integral convolution)
We visualize the pressure distribution in the eye
using colormaps
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT
Tutorial Overview
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Two parts:
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Part 1 (~10 min): familiarize yourself with visualization
software
Part 2 (~25 min): load iris + flow data and visualize them
IGERT on CFD
Louisiana State University
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Credits
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References:
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http://en.wikipedia.org/wiki/Glaucoma
C. Ross et al. Ocular Biomechanics and Biotransport. Annu. Rev.
Biomed. Eng. 2004.
Ian Albert. Anatomy of the Eye.
http://ian-albert.com/graphics/anatomy.php
Moore, Keith L. Moore. Essential Clinical Anatomy, 2nd Edition.
LWW, 2002. 8.6.3
National Eye Institute.
http://www.nei.nih.gov/photo/search/keyword.asp?keyword=glauco
ma
http://en.wikipedia.org/wiki/Vector_%28spatial%29
http://www.calstatela.edu/faculty/acolvil/plates/magnetic_field.jpg
3D Turbulent flow over a car.
http://www.cmis.csiro.au/cfd/fem/car/index.htm
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Credits
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References (continued):
9.
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Simulation Datasets:
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G. Erlebacher . Texture and Feature based Visualization.
http://www-hagen.informatik.uni-kl.de/vis06tutorial/materials/erlebacherVis06slides.pdf
Dr. Anvar Gilmanov
Eye Flow Movie:
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Farid Harhad
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT
Thank you 
IGERT on CFD
Louisiana State University
www.cct.lsu.edu/IGERT