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National Alliance for Medical Image Computing Diffusion Weighted MRI.

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Presentation on theme: "National Alliance for Medical Image Computing Diffusion Weighted MRI."— Presentation transcript:

1 National Alliance for Medical Image Computing Diffusion Weighted MRI

2 National Alliance for Medical Image Computing MRI Processing for Schizophrenia Diffusion MRI: –Tensor computation and display. –Diffusivity measures. –Fiber tracking. Diffusion and Morphological combined: –Non linear registration of DTMRI to DTMRI. –Coregistration of structural MRI to DTMRI.

3 National Alliance for Medical Image Computing Diffusion Imaging S. Maier and M. Kubicki In an isotropic medium (inside a glass of water for example) water molecules naturally move according to Brownian motion. In biological tissues however the diffusion is very often anisotropic. For example a molecule inside the axon of a neuron has a low probability to cross a myelin membrane. Apply gradient in a given direction dark regions correspond to where non Brownian motion has occured.

4 National Alliance for Medical Image Computing DTI allows researchers to quantify the diffusion of water in brain tissue Diffusion for each image voxel is described by 3 perpendicular vectors Isotropic diffusion occurs when there is no restriction to water movement (e.g., ventricles, CSF) Anisotropic diffusion occurs when water movement is restricted to one primary direction (e.g., myelinated fibers) Diffusion Tensors & Anisotropy

5 National Alliance for Medical Image Computing Anisotropy Left: Conventional T2W image does not show white matter fiber tracts in the brain. Middle: Anisotropy map highlights the white matter bundles in the brain. Right: The z-map high intensity regions correspond to large out of plane diffusion.

6 National Alliance for Medical Image Computing Fractional Anisotropy Difference in eigenvalues Directional diffusion Mean Diffusivity Addition of eigenvalues Overall diffusion Diffusivity & Fractional Anisotropy

7 National Alliance for Medical Image Computing Number of fibers Size of fibers Myelination of fibers Directionality of Fibers Diffusivity and FA help determine the number, size and myelination of fibers, whereas only FA gives information about directionality. High Diffusivity Low FA High FA Low Diffusivity High Diffusivity Low FA High FA Low Diffusivity High Diffusivity Low FA High FA Low Diffusivity Low FA Same Diffusivity High FA Same Diffusivity Interpreting Diffusivity and FA

8 National Alliance for Medical Image Computing Fiber Tracking

9 National Alliance for Medical Image Computing Axonal Fibers Using 3T MR-DTI Hae-Jeong Park, Ph.D. Whole-Brain Tractography

10 National Alliance for Medical Image Computing Automated tools separate fibers on the basis of their shape and projections Fiber Clustering

11 National Alliance for Medical Image Computing Fronto-temporal connections uncinate fasciculus (blue) inferior occipito-frontal fasciculus (yellow) IOCC rarely seen in the literature (from Gray’s Anatomy)

12 National Alliance for Medical Image Computing Other applications: Neurosurgery, Brain Tumors

13 National Alliance for Medical Image Computing White matter fiber tracts and Schizophrenia There are widespread gray matter deficits reported in MRI structural studies, but fewer reports of white matter abnormalities. Functional abnormalities are reported in different brain regions and different systems using fMRI and PET. Several theories link schizophrenia with disconnection between different brain regions.

14 National Alliance for Medical Image Computing Cingulum Bundle The most prominent connection between limbic structures. Consolidates information by interconnecting thalamus, prefrontal, parietal, temporal lobes (including amygdala, hippocampus and parahippocampal gyrus) with cingulate gyrus. M. Kubicki

15 National Alliance for Medical Image Computing Schizophrenia related symptoms most frequently linked with cingulate dysfunction Thought disorder Disorganized behavior Hallucinations Flattening of affect Delusions Lack of attention M. Kubicki

16 National Alliance for Medical Image Computing Coronal sections of diffusion tensor maps show cingulate fasciculi (out of plane diffusion component- coded in orange)(arrows), above the corpus callosum (in plane component- coded in blue). Patient with schizophrenia on the left, comparison subject on the right. Note the difference in area of the bundle. M. Kubicki Anisotropy Analysis

17 National Alliance for Medical Image Computing M. Kubicki Relative anisotropy within cingulate fasciculus Diffusion anisotropy within the left cingulum bundle in schizophrenia group was 7.4 % lower than in normal comparison subjects (mean of the percentage difference for all eight slices), while diffusion anisotropy on the right side within the CB in schizophrenics was only 2 % lower than in normal comparisons.

18 National Alliance for Medical Image Computing Fiber Tractography H.J. Park

19 National Alliance for Medical Image Computing Fiber Clustering H.J. Park

20 National Alliance for Medical Image Computing Fiber Tractography H.J. Park

21 National Alliance for Medical Image Computing Research Challenges Diffusion Sequences and Image Resolution. Fiber Tractography. White Matter Segmentation. Statistical Analysis. Current Region Of Interests: –Superior Temporal Gyrus. –Uncinate Fasciculus. –Cingulate Bundle. –Arcuate Fasciculus.

22 National Alliance for Medical Image Computing STEP 1 STEP 2 Initial coarse registration done manually with Slicer Alignment Module. no gradient DTIgray-aligned SPGR + Automatic fine registration using registration module, with Mutual Information as the registration metric. Coregistration of MRI and DTMRI

23 National Alliance for Medical Image Computing Non Linear Registration Module Alexandre Guimond, Lifeng Liu (CNI), Matthan Caan (LMI).

24 National Alliance for Medical Image Computing Coregistration: Qualitative Evaluation. Magenta: MRI (SPGR) Green: DTMRI (T2 baseline)

25 National Alliance for Medical Image Computing Coregistration: Pilot Study Results Measurements: FA: Fractional Anisotropy, AA: Absolute Anisotropy, RA: Relative Anisotropy, ADC: Apparent Diffusion Coefficient. Kang-Uk Lee


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