NAMIC: UNC – PNL collaborationNAMIC: UNC – PNL collaboration - 1 - October 7, 2005

Quantitative Analysis of Diffusion Quantitative Analysis of Diffusion Tensor Measurements along White Tensor Measurements along White Matter TractsMatter Tracts

Postdoctoral fellow,Postdoctoral fellow,Dept of Computer Science Dept of Computer Science and Psychiatry,and Psychiatry,UNC-Chapel HillUNC-Chapel Hill

Isabelle CorougeIsabelle Corouge

NAMIC: UNC – PNL collaborationNAMIC: UNC – PNL collaboration - 2 - October 7, 2005

Diffusion Tensor MRI (DT MRI)

• Reveals white matter structure

Gray matter

White matterCourtesy of Susumu Mori, JHU

DT MRI

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Diffusion of Water Molecules

• Diffusion of water moleculesFrom Beaulieu[02]

• Isotropic vs Anistropic diffusion• Underlying structures of the tissues

– Faster diffusion along fibers than perpendicular to them– Water diffusion anisotropy used to track fibers, estimate white matter integrity

(v, )

(v, )

(v, )

Isotropic Diffusion

vi : principal directions of diffusion

i : associated diffusivities

• Tensor model

Anisotropic Diffusion

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Tensor field

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Diffusion Properties

• Mean diffusivity (MD) • Fractional anisotropy (FA)

3MD 321

Isotropic diffusion

Highly directional

diffusion

0 1Low High

Whitematter

Cerebrospinalfluid

Tensor size 23

22

21

231

232

221 )()()(

21FA

Tensor shape

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DTI Analysis in Clinical Study• One concept: Region-based Analysis

• Co-registration of DTI

• Registration of DTI of each subject with:

• structural MRI

• segmentation maps

• lobe parcellation

• user-defined ROIs

• Statistical analysis per ROI

Group 1

Group 2

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Alternative Concept

• Quantitative Analysis of Fiber Tracts– Fiber-tract oriented analysis– Measurements across/along fiber bundles with complex geometry– Statistics of diffusion properties (FA,MD)– Statistics of tensors (non-Euclidean metric)

• Analysis scheme

Tracking/Clustering

Selection FA FA along tract

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Fiber Tracking & Clustering into Bundles

Fornix clusterLongitudinal fasciculus(2312 streamlines)

6 clusters

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Diffusion Properties: Adult vs NeonateAd

ult

Neo

nate

FA FA: Mean ± σ

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Diffusion Properties: Adult vs NeonateAd

ult

Neo

nate

MD MD: Mean ± σ

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Example: Early Brain Development Study

• White Matter Diffusion Corpus Callosum

– Extraction and clustering of genu and splenium bundles– Measurement of diffusion properties in cross-sections along the

bundles– Selection of center and left/right off-center locations

NAMIC: UNC – PNL collaborationNAMIC: UNC – PNL collaboration - 12 - October 7, 2005

WM Diffusion of Neonates: Genu Tract

• DTI properties measured at midsagittal position and +/- 21 mm

Genu: FA at 0 and at distance 7

00.10.20.30.40.50.60.7

250 300 350 400

MGestAge

FA

FA at 0

FA at dist 7Linear (FA at 0)Linear (FA at dist 7)

21mmGenu: ADC at 0 and at distance 7

0

5

10

15

20

250 300 350 400

MGestAge

ADC

ADC at 0

ADC at dist 7

Linear (ADC at 0)

Linear (ADC at dist7)

21mm

Genu Diffusion Tensor EV: Midsagittal

0

5

10

15

20

25

250 300 350 400

MGestAge

Lam

bda

Lbd1 at 0Lbd2 at 0Lbd3 at 0Linear (Lbd1 at 0)Linear (Lbd2 at 0)Linear (Lbd3 at 0)

Genu Diffusion Tensor EV: Distance 7

0

5

10

15

20

25

250 300 350 400

MGestAge

Lam

bda

Lbd1 at 0Lbd2 at 0Lbd3 at 0Linear (Lbd1 at 0)Linear (Lbd2 at 0)Linear (Lbd3 at 0)

21mm

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White Matter Diffusion Corpus Callosum

Diffusion tensor representation at the midsagittal plane and off-center (24mm along bundles).

• Tensors get “thinner” → less diffusivity across fibers → more structure, ev. marker for maturation

• Genu shows change, but not splenium

280d GestAge at MRI 360d GestAge at MRI

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• Genu and splenium

Tensor Statistics: Neonate to 1 year

MD MD

FA FA

Neonate 1 year old

Neo

nate

1 ye

ar o

ld

Neonate1 year old

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Tensor Statistics: Neonate to 1 year

Genu

Splenium

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In Practice… the Tools !

FiberTracking FiberViewer

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Demo

• Data: Brockton VA/Harvard – Case HUVA00102397– Resampled to isotropic resolution (2x2x2mm3)– Tracts: cingulate, motor, genu, splenium,…

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Fiber Tracking and Fiber Viewer

• Easy to use and easy to learn• Download: http://www.ia.unc.edu/dev • Online tutorial (same url)

• Compatibility Slicer/FiberViewer

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Acknowledgements

• The team– Guido Gerig (UNC)– Casey Goodlett (UNC)– Weili Lin (UNC)– Sampath Vetsa (UNC)– Tom Fletcher (Utah)– Xiadong Tao (GE)– Rémi Jean– Matthieu Jomier (France)– Sylvain Gouttard (France)– Clément Vachet (France)

• Software development– ITK, VTK, Qt– Julien Jomier (UNC)