2002 CITE Research Symposium The Role of Information Technology Coordinator
2002 MIRL Symposium
description
Transcript of 2002 MIRL Symposium
2002 symposium 1
Craig Goodrich
2002 MIRL Symposium
COMPUTER SIMULATION
CAROTID
ATHEROSCLEROTIC
PLAQUE IMAGING
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Topics of Discussion
Why do a computer simulation? Carotid anatomy Atherosclerotic disease Magnetic resonance imaging Implementation of model Results
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Why do a computer simulation?
Truth standard difficult for human imaging
Animal models User determines truth with
computer model
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Arterial wall anatomy Tunica Interna
layer of endothelial cells and elastic fibers
Tunica Mediasmooth muscle cells (SMC) in framework of loose connective tissue
Tunica Externa (adventitia) connective
tissue sheath mostly collagen, with scattered elastin and SMC – blends with adjacent tissues anchoring vessel to them
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Atherosclerotic development High lipid levels in artery -> monocytes become filled
with lipids (now called foam cells) Foam cells attach to endothelium and release growth
factors causing SMC to grow. Monocytes invade, migrating between endothelial
cells. Monocytes, SMC, endothelial cells begin phagocytization of fat resulting in plaque (which projects into lumen).
Endothelial cells become swollen with lipids and gaps appear in endothelial lining. Platelets begin sticking to exposed collagen fibers which leads to clot.
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atherosclerotic disease
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Magnetic Resonance Imaging
Proton magnetic moment Precession depends on field
strength Appropriate manipulation of field
(i.e. linear field gradients) -> image Image contrast depends on proton
density, relaxation, acquisition timing
Motion degrades image quality
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Example MRA images
T1 weighted
Proton density weighted (PD)
Time-of-flight (TOF)
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20 phase/heartbeat phase contrast MRA
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Modeled anatomy
Lumen – determined from phase contrast images
Endothelium – 1 pixel layer Tunica Interna – 6 pixel layers Tunica Media - 21 pixel layers Tunica Externa – 9 pixel layers
(probably should be thicker)
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Proton Density Anatomical Computer model
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Modeling disease
Foam cells Lipid layer Fibrous
plaque Thrombus
13.5%
62% 132%
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MRI simulationusing IDL
Read imaging parametersTR, TE, K_fill, fnecho_lim, theta
Read tissue parametersT1, T2, PD
Read masks for tissue typesbackground (assume muscle)vessel wall components
Determine type of imaging sequence and call subroutine
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Spin echo subroutine1. T1 & T2 correct each tissue mask2. multiply each mask by PD3.For loop for each time phase
a) cut hole in neck mask for vessel structure b) add all tissue masks c) FFT assembled anatomy d) truncate 40962 array to 5122 array (simulates continuous -> discrete) e) store in temporary Kspace array (kx,ky,t)
4. Sequentially fill Kspace as function of TR & HR
5. Add T2* attenuation6. Inverse FFT for final image and return image
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Results
Simulatedphase artifact
Anatomy model Simulated PD images
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Future Work Determine thickening threshold for plaque detection Other contrast models
T2 weightedT1 weightedTOF
Add other anatomy (including movement) Add blood flow Add other k-space trajectories Coil sensitivities Noise, better PD, T2, T1 estimates ……….. Etc.