high angular diffusion imaging and its visualization…
DESCRIPTION
High Angular Diffusion Imaging and its Visualization…. Limitations of DTI Why HARDI is better?!? Different HARDI models My ideas and current work. Underlying philosophy in DTI. S i. S 0. 1 r 1. 1 r 1. 2 r 2. 1 r 2. From probability to diffusivity. - PowerPoint PPT PresentationTRANSCRIPT
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High Angular Diffusion Imaging and its Visualization…
• Limitations of DTI
• Why HARDI is better?!?
• Different HARDI models
• My ideas and current work
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Underlying philosophy in DTI
S0
Si
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From probability to diffusivity
• DTI: D(g) = D P(r) = Gaussian
~2µm
2 –
3 o
rders
of
mag
nit
ud
e
diff
ere
nce
1-2mm
1r1
2r2
1r1
1r2
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Application - DTI
DTITool, BMIA group TU/e
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• What if…– Measure > 6(20) gradient directions– Give more time to the molecules to do
their job
• What if…– Measure: 200-300 gradient directions– Use high b-values: <2000s/mm2 (w.r.t
gradient strength and effective time)
Different approaches
= HARDI
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HARDI
• Many different approaches– DSI , q-ball– High-order tensor models w.r.t. ADC– SH representation– PAS-MRI– Multi-compartment models etc..
• All in common: avoid Gaussian model fitting
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Reality check…
• Long (more complicated) acquisition scheme
• Popular for phantom data and simulations
• Tricky mathematical models• Non-intuitive visualization
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Reality check…
• Scanning time ~0.5h (and much more!)• Phantoms like it – people don’t like it!• Mathematical models:
PDF = mixture of Gaussians
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Reality check…
• Scanning time ~0.5h (and much more!)• Phantoms like it – people don’t like it!• Mathematical models:• m
SH representation of ADC
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Reality check…
• Scanning time ~0.5h (and much more!)• Phantoms like it – people don’t like it!• Mathematical models:
HOT representation of ADC
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…and of course Visualization issues
[Tuch, PhD Thesis 2002]
[Ozarslan, MRM 2003]
[Liu, MRM 2004 ]
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My current work, ideas, struggles…
• Comparing most promising methods (w.r.t. feasibility on vivo data) and improve it– DOT and q-ball
• Answer the mysterious 42 question: “How high should be the “high” b-value?”
• DTI is not dead! Combining with HARDI. Define measure where 2nd order tensor is sufficient!
• Segmentation on HARDI data.
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• More intuitive HARDI visualization => doctors don’t like glyphs• Fiber tracking on HARDI
• Combining different modalities– Use of fMRI activation zonesas seeding regions for whitematter tractography
My current work, ideas, struggles…
[Hardenbergh, IEEE Vis 2005]
[INRIA-McGill]
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Multi-fieldity in HARDI
• Multiple measurements over same domain
• High-dimensional data• High-order mathematical
models (HOT and SH)• Combining HARDI+fMRI
=>Jorik• Sufficient order w.r.t.
encapsulated information=> Stef