Reconstruction and Visualization of Fiber and Laminar Structure of the
Nov 2, 2007 - Color Encoding. â Fiber Direction. â Tensor Visualization. 1. ... a portion of ellipsoid. Texas Heart Institute : http://www.tmc.edu/thi/anatomy.html ...
Reconstruction and Visualization of Fiber and Laminar Structure of the Human Heart Damien Rohmer Lawrence Berkeley Laboratory Supervisor : Grant T Gullberg 11/02/07
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Summary 1. Structure of the heart – Geometry of the heart – Fiber Organisation – Sheet organization
2. Diffusion Tensor – Introduction – Role – Available Data
3. Visualization Methods – Color Encoding – Fiber Direction – Tensor Visualization
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1. Fiber Tracking – – – – –
Integration Step Interpolation Filtering Sense of the propagation Results
2. Sheet Structure – Method – Results
3. Conclusion
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Summary 1. Structure of the heart – Geometry of the heart – Fiber Structure • General orientation • Physical Constitution • Spatial Arrangement – Sheet organization • Spatial Arrangement • Physical Constitution – Role of the study
1. Structure of the heart • Geometry of the heart – Approximate by a portion of ellipsoid
Texas Heart Institute : http://www.tmc.edu/thi/anatomy.html
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1. Structure of the heart • Fiber Structure – General Orientation
Microscopic view of the cells : myocytes
Helicoidal Structure
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1. Structure of the heart • Fiber Structure – Physical Constitution Constitution of the fibers and myocardial Collagen :
•Disc junctions : continuity of information between cells •Role of Collagen : prevent slipage, rupture and overstretch. Mainly Type I and III (62%).
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1. Structure of the heart • Fiber Structure – Spatial Arrangement (I)
Direction Across the wall
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1. Structure of the heart • Fiber Structure – Spatial Arrangement (II)
•Fiber direction changing from +60º (epicardium) to -60º (endocardium) across the wall •Define fiber angle α
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1. Structure of the heart • Sheet Structure – Spatial Arrangement
Higher 3 Dimensional Structure •Arrangement of fibers in Sheets stacked form apex to base •Define a sheet angle β
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1. Structure of the heart • Sheet Structure – Physical Constitution
•Physical separation by Perimysial Collagen. Mainly Type I (72%) and III. •Fibers lie in the sheet
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1. Structure of the heart • Role of the Study Fiber
Goal
Reasons
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Sheet
•Visualizing the precise orientation of the fiber •Comparing with the standard model (+60º/-60º) •Study interesting regions like apex: compare with Band Theory (TorrentGuasp)
•Visualization of the laminar structure.
•Twisting motion of the heart. •Precise model of the morphology. •Electrical Model.
•Better understanding of the structure •Orthotropic distribution of Stress and Strain •Remodelling after infarct 11
Summary 1. Structure of the heart 2. Diffusion Tensor – Introduction • Einstein formulation of diffusion • Eigenvalue decomposition – Role • Largest Diffusion direction • Other directions • Overview of the vectors – Available data • Data Set • Normal MRI • Diffusion MRI
Structure of the heart Diffusion Tensor Visualization Methods Fiber Tracking – – – –
Introduction Integration Step Interpolation Filtering of the data • Noise • MLS Method – Sense of the propagation – Results • Helicoidal wrapping • Smooth fiber angle change • Apex
5. Sheet Structure 6. Conclusion 02/11/07
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4. Fiber Tracking • Introduction
trajectory Seed = starting point
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4. Fiber Tracking • Integration Step
ODE form : first order, non-linear
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Use Runge-Kutta : order 5 (Dormand-Prince)
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4. Fiber Tracking • Interpolation
Known data 02/11/07
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4. Fiber Tracking • Interpolation
Problem of interpolation :
Normalized vectors
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4. Fiber Tracking • Filtering of the data – Noise
Data are noisy
Gaussian filter will destroy the Anisotropy
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4. Fiber Tracking • Filtering of the data – MLS (Moving Least Square) method (I)
Minimization :
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4. Fiber Tracking • Filtering of the data – MLS (Moving Least Square) method (II)
Approximated by a polynome
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4. Fiber Tracking • Filtering of the data – MLS method (III)
Structure of the heart Diffusion Tensor Visualization Methods Fiber Tracking Sheet Structure Conclusion – Fiber Tracking – Sheet Reconstruction
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6. Conclusion • Fiber Tracking
Results
Future Work
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•Smooth Results with MLS •Fit to the model (goes to +90º to -90º)
•Fiber tracking in the whole heart (papillary muscles, right ventricle) •Validation of the Band Theory (TorrentGuasp)
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6. Conclusion • Sheet Reconstruction
Results
•Smooth in the some regions •Correspond to the measurements in those regions
Difficulties And future work
•Geometry is complex (cross section is not always the best direction) •Noise level (inversion, noise at the boundaries) •Need a check on the normal direction
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Acknowledgment • Arkadiusz Sitek • Grant T Gullberg
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