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