analysis and processing of diffusion weighted mri
DESCRIPTION
Analysis and processing of Diffusion Weighted MRI. Remco Duits Anna Vilanova Luc Florack. Tom Dela Haije Rutger Fick. Supervised by : Collaboration : with. Overview of presentation. Short introduction to DW-MRI Enhancement of DW-MRI data Fiber tracking. Diffusion of water. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/1.jpg)
Analysis and processing of Diffusion Weighted MRI
Supervised by:
Collaboration:with
Remco DuitsAnna VilanovaLuc Florack
Tom Dela HaijeRutger Fick
Slide 1 of 31
![Page 2: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/2.jpg)
Overview of presentation
1) Short introduction to DW-MRI2) Enhancement of DW-MRI data3) Fiber tracking
Slide 2 of 31
![Page 3: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/3.jpg)
Diffusion of water
Diffusion is dependent on orientation
Slide 3 of 31
![Page 4: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/4.jpg)
Visualization
4Slide 4 of 31
![Page 5: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/5.jpg)
Goal
Slide 5 of 31
![Page 6: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/6.jpg)
Overview
Raw Data
Water Diffusion Modelling
Tensor(s)Water PDF
Othermodels
Fiber PDF
Fiber Tracking
Clinical Information
Low signal for high diffusion
Slide 6 of 31
![Page 7: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/7.jpg)
Constrained Spherical Deconvolution
Original data(single fiber)
Spherical Deconvolution
ConstrainedSpherical Deconvolution
Slide 7 of 31
![Page 8: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/8.jpg)
Enhancement of PDFs
• PDFs contain information on the direction of water diffusion (water PDF) or fiber distribution (fiber PDF)
• Many models can be converted to a PDF- Often noisy and incoherent
Slide 8 of 31
![Page 9: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/9.jpg)
Rotating coordinate systemz
yx
• diffusion
• diffusio
n
Slide 9 of 31
![Page 10: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/10.jpg)
Evolutions in new frame• Contour Enhancement
Contour Enhancement
Slide 10 of 31
![Page 11: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/11.jpg)
Evolutions in new frame• Contour Completion
Contour completion
Slide 11 of 31
![Page 12: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/12.jpg)
Results
Slide 12 of 31
![Page 13: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/13.jpg)
Results on simple fibertracking
Phantom dataset from the ISBI reconstruction challenge (2013)
• Fibertracking on CSD • Fibertracking on enhanced CSD
Slide 13 of 31
![Page 14: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/14.jpg)
Fiber Tracking
• Problem: find anatomical fibers based on DW-MRI scan– Variants
• Find brain fiber between two areas• Find all fibers that pass through an area
• Mathematical problem? – Multiple options
Slide 14 of 31
![Page 15: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/15.jpg)
Local fiber trackingStreamline tracing:• Compute main
direction of diffusion (AKA: reduce to vectorfield: )
• Integrate along vectorfield from given seedpoint
Slide 15 of 31
![Page 16: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/16.jpg)
Advantages/Disadvantages
• Advantages– Computationally cheap– Easy to implement
• Disadvantages– Error accumulation– Sensitive to noise
Slide 16 of 31
![Page 17: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/17.jpg)
Local method: example
Slide 17 of 31
![Page 18: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/18.jpg)
Global fibertracking• curve
Curvature• Corresponding energy functional
External cost (data) Geodesic energy• Find for given end points/directions
Solved for C(x)=1
Slide 18 of 31
![Page 19: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/19.jpg)
Horizontal curves
Slide 19 of 31
![Page 20: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/20.jpg)
Lifting the optimal curve problem to
The energy functional to minimize
subject to the constraints along the curve:
Slide 20 of 31
![Page 21: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/21.jpg)
Solutions sub-Riemannian geodesics Ghosh&Dela Haije&Duits
Slide 21 of 31
![Page 22: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/22.jpg)
Optimal control problem
Slide 22 of 31
![Page 23: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/23.jpg)
Benefits and disadvantages
• Advantages– Robust to noise– No error accumulation
• Disadvantages– Computationally expensive– Needs more boundary conditions– Can sacrifice local error for global
optimizationSlide 23 of 31
![Page 24: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/24.jpg)
Global method:example
Slide 24 of 31
![Page 25: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/25.jpg)
New idea: combine local and global
• Not global energy minimizers, but limit search to smaller search areas and combine solutions
• Add additional constraints to limit search space– Limit curvature to be below threshold– Do extra constraints change optimal curve
problem?
Slide 25 of 31
![Page 26: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/26.jpg)
Intuition
Slide 26 of 31
![Page 27: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/27.jpg)
Search areaSimulate convection Geodesics to endpoints
Slide 27 of 31
![Page 28: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/28.jpg)
Theoretical benefits• Advantages
– Robust to noise– Computational intermediate– Balance between local and global error– Limits to local or global method for
search area small or large• Disadvantages
– Extra parameters that need to be tuned
Slide 28 of 31
![Page 29: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/29.jpg)
How to find optimum curve?• Minimizer may not exist• Minimizer may not be unique• Different options
– Use Dijkstra to find cheapest path along tree-graph (restricts energy function)
– Try discrete subset of curves– Get an approximate minimizer and
iteratively refine itSlide 29 of 31
![Page 30: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/30.jpg)
Past and Plans• Article published in NM-TMA (feb ‘13)• Enhancement Article published in JIMV• Refine ideas and publish proof-of-concept
to MICCAI conference (June)• Expand for journal article• Visit Berlin to work on new non-linear
enhancement technique (August)
Slide 30 of 31
![Page 31: Analysis and processing of Diffusion Weighted MRI](https://reader035.vdocuments.net/reader035/viewer/2022062323/568164ce550346895dd6f321/html5/thumbnails/31.jpg)
Any questions, ideas or suggestions?
Slide 31 of 31