Segmentation of the left atrial appendage from 3D images
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Transcript of Segmentation of the left atrial appendage from 3D images
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Segmentation of the left atrial appendage from 3D images
Pol Grasland-Mongrain20/04/2009 – 28/08/2009
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Views of the Left Atrial Appendage
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Views of the Left Atrial Appendage
• Variable shapes• 1 to 19 cm3
• Function ?• Has to be ablated sometimes
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Motivation
Current implementation:• LAA is represented as a short trunk in the model• Current framework not flexible enoughto grow into highly variable shape
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Motivation
Motivation of my master thesis:• Addition of an Automatic SegmentationAlgorithm of the Left Atrial Appendagein the Philips Framework
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Plan
I. Current Method at PhilipsII. Actual WorkIII. Results and Future Work
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Philips Aachen method
New Image Segmentation Chain Segmented Image
1. HeartDetection
2. Parametric Adaptation(Similarity)
4. Deformable Adaptation
3. Parametric Adaptation
(Piecewise Affine)
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Philips Aachen method
New Image Segmentation Chain Segmented Image
1. HeartDetection
2. Parametric Adaptation(Similarity)
4. Deformable Adaptation
3. Parametric Adaptation
(Piecewise Affine)
vadap = T[v]E = Eext[T]
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Parametric Adaptation,Deformable Models
• Use External Energy :
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Philips Aachen method
New Image Segmentation Chain Segmented Image
1. HeartDetection
2. Parametric Adaptation(Similarity)
4. Deformable Adaptation
3. Parametric Adaptation
(Piecewise Affine)
Free motion for vadap
E = Eext[v]+ α Eint[v]vadap = T[v]E = Eext[T]
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Deformable Models
• Internal Energy
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Plan
I. Current Method at PhilipsII. Actual Work
1. Segment manually 17 patients LAA2. Modify Philips models
1. Interface Left Atrium - Left Atrium Appendage2. Mesh which inflate
3. Code an automatic mesh-inflation algorithm1. External Energy2. Threshold between LAA – Background3. Internal Energy
III. Results and Future Work
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Plan
I. Current Method at PhilipsII. Actual Work
1. Segment manually 17 patients LAA2. Modify Philips models
1. Interface Left Atrium - Left Atrium Appendage2. Mesh which inflate
3. Code an automatic mesh-inflation algorithm1. External Energy2. Threshold between LAA – Background3. Internal Energy
III. Results and Future Work
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Plan
I. Current Method at PhilipsII. Actual Work
1. Segment manually 17 patients LAA2. Modify Philips model
1. Interface Left Atrium - Left Atrium Appendage2. Mesh which inflate
3. Code an automatic mesh-inflation algorithm1. External Energy2. Threshold between LAA – Background3. Internal Energy
III. Results and Future Work
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Model Modification
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Plan
I. Current Method at PhilipsII. Actual Work
1. Segment manually 17 patients LAA2. Modify Philips model
1. Interface Left Atrium - Left Atrium Appendage2. Mesh which inflate
3. Code an automatic mesh-inflation algorithm1. External Energy2. Threshold between LAA – Background3. Internal Energy
III. Results and Future Work
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External and Internal Energies
Edge-based
Region-based
MeshReference
TriangleRegularization
Curvature N-GonRegularization
External Energy Internal Energy
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External Energy :Edge-Based
• No specific features
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External Energy :Region-Based
•Gray Value Above or Under ?
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External Energy :Region-Growing
•Gray Value Still Above (Under) ?•Already Annotated ?
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External Energy :Region-Growing
Gray Value Still Above (Under) ?Already Annotated ?•Gray Value Still Above (Under) ?•Already Annotated ?
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External Energy :Region-Growing
Gray Value Still Above (Under) ?Already Annotated ?•Gray Value Still Above (Under) ?•Already Annotated ?
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Threshold LAA-Myocardium
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Threshold LAA-Myocardium
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Threshold LAA-Myocardium
oMinimization of classification erroro Stop when Area1 = Area2
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Internal Energy :Mesh Reference
• Updated Mesh
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Internal Energy : Triangle Regularization
• Approximate each triangle by a rotated and scaled equilateral triangle
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Internal Energy :Curvature
• Remove the peaks
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Internal Energy :Curvature
• Remove the peaks
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Internal Energy :N-Gon Regularization
• Approximate each “N-Gon” by a rotated and scaled regular N-Gon
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External and Internal Energies
Edge-based
Region-based
MeshReference
TriangleRegularization
Curvature N-GonRegularization
External Energy Internal Energy
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Plan
I. Current Method at PhilipsII. Actual WorkIII. Results and Future Work
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Results
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Results
• Main problem : loops -> repair
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Results
Specificity = True Pos. /(True Pos. + False Neg.)
Quality = True Pos. /(True Pos. + False Pos.)
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Results
0
20
40
60
80
100
Left Atrial Appendage Inflation ResultsSpecificity = True Pos. / (True Pos. + False Neg.) Quality = True Pos. / (True Pos. + False Pos.)
Sum up: • almost all segmented voxels really belong to LAA• but the mesh doesn’t inflate enough
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Results
(1) (10)
(5)(7)
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Majors Fails
(11) (14)
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Possible future works
• Improve the loop repair :– Freeze vertices– Better correction
• Find a new internal energy ?
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Thank you for your attention !
Any Questions ?