L’Arche Canada’s Audit and Risk Management Plan Presented by: Bernard L’Abbé 2013 General Assembly
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3D Echocardiography: recent advances and
future directions
1 University of Lyon, France
O. Bernard1, D. Barbosa2, M. Alessandrini2,
D. Friboulet1, J. D’hooge2
2 K.U. Leuven, Belgium
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Outline
Context
Basics on image formation
Ultra realistic simulation
Echocardiographic image processing
Future directions
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3D Echocardiographic imaging
In summary
Non invasive modality
Assess mechanical
properties of the heart
such as the strain in
real time
One of the cheapest
modality in 2D and 3D
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Echocardiographic image processing
Clinical useful information
Clinical indices such as the Ejection Fraction (EF)
or the Stroke Volume (SV)
Necessity to perform accurate segmentation
End Diastolic
Volume (EDV)
End Systolic
Volume (ESV)
𝑬𝑭(%) =𝑬𝑫𝑽 − 𝑬𝑺𝑽
𝑬𝑫𝑽∗ 𝟏𝟎𝟎
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Echocardiographic image processing
Clinical useful information
Strain and strain rate measurement
• Opens the door to local cardiac deformation assessment
Necessity to perform motion analysis
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BASICS ON ULTRASOUND IMAGE FORMATION
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Basics on US image formation
2D Ultrasound probe
Phased array transducer
(less than 192 elements)
Delays on each element
Possibility to focalize the
energy in various part of
the medium
y (elevation)
x (lateral)
z (axial)
Width
Pitch
Kerf Height
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Basics on US image formation
Different kind of signals
1
3
2 Rf image
Enveloppe image
B-mode image
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Basics on US image formation
Different kind of signals
1
3
2 Rf image
Enveloppe image
B-mode image Image mostly used in 3D
echocardiography
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Basics on US image formation
3D Ultrasound probe
2D matrix array transducer
(3000 elements involved)
Technical difficulties in
driving all the elements
Impact spatial resolution
Technical difficulties in
scanning the volume of
interest in real time
Impact temporal resolution
Open head of probe
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Basics on US image formation
Image properties
Typical voxel size: 0.80 x 1.00 x 1.00 𝒎𝒎𝟑
Temporal resolution: 20 volumes per second
Long Axis 4 chambers Short Axis Long Axis 2 chambers
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ECHOCARDIOGRAPHIC IMAGE PROCESSING
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Echocardiographic image processing
Image properties
Spatial
No clear contours
Noisy nature (speckle)
Temporal
Speckle decorrelation
Linked to frame rate
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Echocardiographic image processing
Current needs
No real consensus on the accuracy of what we can
extract from this modality
Strong need of evaluation platform for quality
assurance of algorithms applied to this modality for:
• Segmentation
• Motion estimation
• Tissue characterisation
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ULTRA REALISTIC SYNTHETIC ECHOCARDIOGRAPHIC SEQUENCES
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Ultra realistic echocardiographic simulations
State-of-the-art
Ultrasound Simulator
Field II [Jensen et al., 1992]
Cole [Gao et al., 2009]
Creanuis [Varray et al., 2011]
Realistic Simulation
[Gao et al., UMB, 2009]
[Alessandrini et al., ICIP, 2012]
[De Craene et al., IEEE TMI, 2013]
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ULTRA REALISTIC SYNTHETIC ECHOCARDIOGRAPHIC SEQUENCES
BASICS
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Simulator principle
Speckle
pattern
Simulate a realistic point spread
function that characterises the
ultrasound probe
Simulate a medium from a set of
scatterer points with specific
backscattering coefficients
∗
?
How many scatterers ?
Which positions ?
Which amplitudes ?
Which motion ?
sector in degree
depth
in m
m
-40 -30 -20 -10 0 10 20 30 40
20
40
60
80
100
120
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ULTRA REALISTIC SYNTHETIC ECHOCARDIOGRAPHIC SEQUENCES
MOST ADVANCED SOLUTIONS De Craene et al. – Philips Research France
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Most advanced solutions in US simulations
[De Craene et al., TMI, 2013]
Anatomical
model
Obtained from MR segmentation
Electromechanical motion model
Properties
• Realistic motion model
• Need to improve image quality
Contractility Activation [Sermesant et al., TMI, 2013]
Ultrasound simulator
- Inside myocardium: motion derived from the EM model
- Outside myocardium: random scatterers position and motion
- Scatterers amplitudes: simple gaussian distribution
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ULTRA REALISTIC SYNTHETIC ECHOCARDIOGRAPHIC SEQUENCES
MOST ADVANCED SOLUTIONS Alessandrini et al. – Creatis, France
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Most advanced solutions in US simulations
[Alessandrini et al., ICIP, 2012]
Improvement of image quality : Image-based approach
Build a simulation based on a real clinical sequence
Learn the motion to be applied to the scatterers inside
the myocardium from the real sequence
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Most advanced solutions in US simulations
[Alessandrini et al., ICIP, 2012]
Improvement of image quality : Image-based approach
Build a simulation getting inspired by a real clinical
sequence
Learn the scatterers amplitudes from the real sequence
𝐴 = 10
𝐾20𝐼
𝐼𝑀𝐴𝑋− 1
• A: scatterers amplitude
• I : real image intensity
• K: controls dB range of the
resulting image
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Most advanced solutions in US simulations
[Alessandrini et al., ICIP, 2012]
Real clinical recording
Simulated sequence
Reference motion
Properties
Simulation of surrounding structures
Simulation of image artifacts
No motion model
Only implemented in 2D
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ULTRA REALISTIC SYNTHETIC ECHOCARDIOGRAPHIC SEQUENCES
FUTURE DIRECTIONS
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Future directions in US simulations
How to still improve simulations ?
Merge the model-based simulation with the image-
based one
Anatomical + Electromechanical models
Dedicated registration algorithm
Real clinical recording
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Ultra realistic echocardiographic simulations
Future directions
Quantitative comparison of existing 3D
segmentation, motion and strain estimation
techniques
Improving the heart models for the generation of
a set of controlled pathological cases
Creation of a publicly available library of
sequences including clinically relevant cases
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ECHOCARDIOGRAPHIC IMAGE PROCESSING
FEATURE EXTRACTION
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Feature extraction
What kind of features ?
Information support: B-mode image
Most accessible and time efficient support
Edge information
Monogenic signal
Region information
First order statistics computed locally
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ECHOCARDIOGRAPHIC FEATURE EXTRACTION
MOST ADVANCED SOLUTIONS Noble et al. – Institute of Biomedical
Engineering, U.K.
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Most advanced algorithms in feature extraction
Monogenic signal in few words
Extension of the analytic signal in n-D
Assumption: local image patches have intrinsic
dimensionality one
Efficiently extract local amplitude, local orientation,
local phase and instantaneous frequency in the
direction of maximum energy
𝒄𝒐𝒔(𝝋 𝒙 )
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Most advanced algorithms in feature extraction
[Rajpoot et al., ISBI, 2009]
Exploit the monogenic signal for edge detection in
3D echocardiography images
Feature asymmetry (FA) operator for phase-
congruency measure in the particular case of step
edges
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Most advanced algorithms in feature extraction
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Most advanced algorithms in feature extraction
[Stebbing et al., MEDIA, 2013]
Machine learning based on boundary fragment model
to classify the different detected edges
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ECHOCARDIOGRAPHIC IMAGE PROCESSING
SEGMENTATION
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3D Echo segmentation
Echocardiographic image processing
Left ventricle
Full myocardium
3D Transesophageal
4 chambers
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3D Echo segmentation
Echocardiographic image processing
Left ventricle
Full myocardium
3D Transesophageal
4 chambers
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Echocardiographic image processing
State-of-the-art in 3D Left Ventricle segmentation
Without prior
Statistical Shape/Appearance Model Leung, ISBI 2010 Zhang, UMB 2013 Butakoff, FIMH 2011
With prior
Supervised tissue classification Lempitsky, FIMH2009 Verhoek, MLMI2011
Machine learning from large databases Yang, IEEE TMI 2011
Graph Cuts Juang, ISBI 2011
Dynamic Programming van Stralen, Academic Radiology 2005
Deformable models
Simplex Meshes Nillesen, Phy. Med. Biol. 2009
Level-sets Rajpoot, MedIA 2011
B-Spline Explicit Active Surfaces Barbosa, UMB 2013
Kalman-based surface tracking Dikici, MICCAI 2012
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Echocardiographic image processing
State-of-the-art : Performance evaluation
Study Year #
Exams Analysis time (s)
EDV MAD (μ±σ mm) R BA (μ±2σ ml)
Van Stralen 2005 14 90+Manual Init 0.93 -10±60 X
Nillesen 2009 5 X X 6.7±4.6 X
Lempitsky 2009 14 2-22 X X X
Leung 2010 99 X 0.95 1.5±40 2.91±1.0
Juang 2011 4 X X X 2.4±3.2
Rajpoot 2011 34 X X -5.0±49 2.2±0.7
Butakoff 2011 10 X X 6.4±14 1.6±1.1
Butakoff 2011 20 X X 3.1±47 1.8±1.9
Verhoek 2011 25 2 X X X
Yang 2011 67 1.5 X 1.3±12 1.3±1.1
Dikici 2012 29 0.08 X X 2.0±X
Barbosa 2013 24 1 0.97 -2.4±23 X
Zhang 2013 50 45-60 0.83 4.2±35 3.2±1.0
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Echocardiographic image processing
State-of-the-art : Performance evaluation
Study Year #
Exams Analysis time (s)
EDV MAD (μ±σ mm) R BA (μ±2σ ml)
Van Stralen 2005 14 90+Manual Init 0.93 -10±60 X
Nillesen 2009 5 X X 6.7±4.6 X
Lempitsky 2009 14 2-22 X X X
Leung 2010 99 X 0.95 1.5±40 2.91±1.0
Juang 2011 4 X X X 2.4±3.2
Rajpoot 2011 34 X X -5.0±49 2.2±0.7
Butakoff 2011 10 X X 6.4±14 1.6±1.1
Butakoff 2011 20 X X 3.1±47 1.8±1.9
Verhoek 2011 25 2 X X X
Yang 2011 67 1.5 X 1.3±12 1.3±1.1
Dikici 2012 29 0.08 X X 2.0±X
Barbosa 2013 24 1 0.97 -2.4±23 X
Zhang 2013 50 45-60 0.83 4.2±35 3.2±1.0
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ECHOCARDIOGRAPHIC IMAGE SEGMENTATION
MOST ADVANCED SOLUTIONS Barbosa et al. – Creatis – KULeuven,
France, Belgium
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Most advanced algorithms in segmentation
[Barbosa et al., UMB, 2013]
Formalism specifically dedicated for near real time
3D segmentation
Exploit equivalence under specific constraint
between implicit and explicit representation inside
the variational framework of level-set methods
Solve a 3D problem in a 2D space (dimensionality
reduction)
Segmentation performed through a B-Spline
formulation in order to decrease even more
computational time
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Most advanced algorithms in segmentation
[Barbosa et al., UMB, 2013]
Interface evolution corresponds to a succession of
simple separable convolutions
with: 𝑬𝒆𝒙𝒑 Energy to minimize
𝒄[𝐤] B-Spline coefficients
𝒈 (𝒙∗) data attachment term
𝜷𝒉 B-spline function
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Most advanced algorithms in segmentation
Au et Av : interior and exterior regions
used for the computation of the
local means
𝐱∗ ∈ ℝ2with coordinates {𝑥1, 𝑥2}
𝑰 (𝐱∗) restriction of 𝑰 to interface 𝚪
B(x,y)
x
[Barbosa et al., UMB, 2013]
Evolution equation
With
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Most advanced algorithms in segmentation
Results
Validation performed on 24 patients among whom
80% present different cardiac pathologies
All data were manually segmented by 3 experts
Corr. Coeff: 0.97 (EDV), 0.97 (ESV), 0.91 (EF)
Average Cpu time per volume: 25 ms
2.9-GHz 4-Core laptop, with 7.7GB Memory running Fedora
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ECHOCARDIOGRAPHIC IMAGE PROCESSING
MOTION ESTIMATION
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Motion estimation
State-of-the-art in motion estimation
Many algorithms have been proposed
The most well known is based on block matching
Most of them are based on intensity conservation
• Assumption: a moving structure should conserve
its brightness appearance between two consecutive time instants
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Motion estimation
State-of-the-art in motion estimation
Without prior
Statistical model Wang, STACOM, 2010 Leung, UMB, 2011
With prior
Mechanical model Papademitris, MEDIA, 2001 Sermesant, MICCAI, 2001
B-Spline transformation Heyde, STACOM, 2013 De Craene, MEDIA, 2012 Piella, STACOM, 2013
Optical flow Alessandrini, TIP, 2013 Tautz, STACOM, 2013 Mansi, IJCV, 2011
Block-matching Isla, JASE, 2011 Crosby, UMB, 2009 Seo, JACC, 2011
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Motion estimation
MICCAI’12 Challenge [De Craene et al., TMI, 2013]
Synthetic motion from an Electro-Mechanical model
Simulate normal and pathological cases (13 patients)
Comparison of 5 methods
• 2 B-Spline transformation based methods
• 3 Optical flow based methods
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Motion estimation evaluation
Magnitude errors
Globally over a cardiac cycle
For each time instant in the sequence
Motion estimation
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Motion estimation
MICCAI’12 Challenge
Average magnitude error over a cardiac cycle
Ischemic sub groups Dyssynchrony sub groups
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Motion estimation
MICCAI’12 Challenge
Average magnitude error over a cardiac cycle
Ischemic sub groups Dyssynchrony sub groups
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ECHOCARDIOGRAPHIC MOTION ESTIMATION
MOST ADVANCED SOLUTIONS Heyde et al. – KULeuven, Belgium
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Most advanced algorithms in motion estimation
[Heyde et al., FIMH 2013]
Free-form deformations in 3D to estimate motion
Model displacement in B-Spline space
Registration performed in a recursive minimization way
𝒅𝑡→𝑡+1 𝒙 = 𝒄[𝑘, 𝑙]𝛽𝜎𝑥 𝑥 − 𝑘 𝛽𝜎𝑦 𝑦 − 𝑙
1,𝑁𝑘 ,[1,𝑁𝑙]
𝐸 = 𝑆 𝑰𝒕, 𝑰𝒕+𝟏, 𝒄 + 𝜆𝑅(𝒄)
with: 𝑬 Energy to minimized
𝑺 Sum of Square diff. measurement
𝑹 Regularization function
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Most advanced algorithms in motion estimation
[Heyde et al., FIMH 2013]
Illustration in 2D
Extension in 3D
Derivation of
motion and strain
Image warping Registration
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Most advanced algorithms in motion estimation
[Heyde et al., FIMH 2013]
Anatomical shaped control grid
Less control points (efficiency)
Naturally enforce smoothness in the physiologically
relevant directions
Anatomically shaped control grid Regular control grid
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Most advanced algorithms in motion estimation
Acute myocardial infarct
On going results
Feasibility on 6 clinical data
3 healthy patients + 3 with pathologies
(Acute myocardial infarct)
Average Cpu time per volume:
4 minutes
2.8-GHz 4-Core laptop, with 8.0GB
Memory running Windows
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FUTURE DIRECTIONS
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Future directions
Key point: image quality
Deeply depend on the capacity to improve or not
3D echocardiographic image quality
Scenario 1: No real improvement
Needs of quantifying what
exactly we could extract from
this modality
Needs of going further in
adapted image processing
Needs of doing real time
processing
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Future directions
Key point: image quality
Deeply depend on the capacity to improve or not
3D echocardiographic image quality
Scenario 2: Improvement is possible
Needs of working on the
acquisition process itself
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Future directions
3D echocardiographic acquisition improvements
Strong efforts are currently made to improve image quality
Temporal resolution
Compressed sensing in ultrasound
[Wagner et al., IEEE TSP, 2012]
Spatial resolution
Fourier ultrasound imaging
[Garcia et al., IEEE UFFC, 2013]
Modify the image to facilitate motion estimation
Ultrasound-tagging imaging
[Liebgott et al., IEEE UFFC, 2013]
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Future directions
Ultrasound-tagging [Liebgott et al., UFFC 2013]
Main idea: reproduce the principle of tagged MR
imaging in ultrasound
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Future directions
Classical B-mode image US-tagging
Tagged ultrasound imaging [Liebgott et al., UFFC 2013]
http://www.creatis.insa-lyon.fr/us-tagging/
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THANK FOR YOUR ATTENTION