Centre for Biomedical and Healthcare Engineering CNRS UMR 5307
Mr Aaron Romo, Prof Stéphane Avril, Dr Pierre Badel, Dr Ambroise Duprey, Prof
Jean-Pierre Favre, Prof Sam Evans
Full-field strain measurement and material
identification in soft tissue biomechanics
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Institut Mines Telecom
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Center for Biomedical and Healthcare Engineering Centre Ingénierie et Santé
Campus with hospital, medical school, prevention center, college of engineering and companies manufacturing
medical devices
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4 topics
22 permanent staff 35 postgraduate
students and postdocs
Soft tissue
biomechanics
Biomaterials for bone
replacement Healthcare
engineering
Biotoxicity of inhaled
nanoparticules
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Biomechanics of soft tissues
The aim is to employ biomechanical models to adapt the treatments of cardiovascular and osteoarticuar diseases to each patient
Orthèses fonctionnelles
Orthèses de rééducation
Orthèses prophylactiques
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Today’s talk…
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
ascending aorta
descending aorta
(thoracic aorta and abdominal aorta)
arch of aorta ▶ a local dilation of the aorta
due to aortic wall weakening
a fatal medical emergency aneurysm rupture
Aortic aneurisms
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Aortic aneurisms
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
INDIVIDUAL
PREVENTION OF
AA RUPTURE FROM
A BIOMECHANICAL
POINT OF VIEW???
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Quantify the risk of rupture for each patient…
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
[McGloughlin T. Biomechanics and mechanobiology of aneurysms. 2012, Springer
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2 IMPORTANT QUESTIONS
What are the patient-specific material properties of the
tissue?
What is the patient-specific strength of the tissue?
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
BIOMECHANICAL EXPERIMENTAL
APPROACHES
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Tensile rupture mode
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
[Duprey et. al., In-vitro characterisation of physiological and
maximum elastic modulus of ascending thoracic aortic aneurysms using uniaxial tensile testing, Eur. J. Vascular &
Endovascular Surgery, 2010]
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Arteries: a complex structure and
behavior
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Biomechanical comparison of aneurismal and healthy tissue
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Vorp DA, Schiro BJ, Ehrlich MP, Juvonen TS, Ergin MA, Griffith BP. Effect of aneurysm on the tensile strength and biomechanical behaviour of the ascending thoracic aorta. Ann Thorac Surg 2003; 75(4):1210-4.
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Need of biaxial tension
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Sacks MS. Biaxial mechanical evaluation of planar biological materials. J. Elast. 61:199–246, 2000
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
W < 10 mJ/cm 2
Sommer G, Gasser TC, Regitnig P, Auer M., Holzapfel G.A. Dissection properties of the human aortic media: an experimental study. ASME J Biomech Eng 2008; 130:021007.
Delamination properties…
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Lack of local analyses
Where and how does the rupture initiates?
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
MATERIALS AND
METHODS
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Materials
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
inflation device cylinder
pressure gage
in vivo loading environments
(biaxial stress state due to internal pressure) can be generated
Inflation test
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
camera
Instron machine protector
Undeformed Deformed
x y
tracks the gray value pattern
in each subset during deformation
Digital image stereocorrelation
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Theory of finite deformation
Deformation gradient F
Green-Lagrange strain tensor E = 1/2(C - I) right Cauchy-Green tensor C = F T F
Ux Uy Uz
from the undeformed and deformed
coordinates of each measurement data point
Assumption: plane stress
homogeneous initial thickness incompressibility
Measured displacement fields
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Derivation of the strain fields
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
ℎ = ℎ 0
𝑭 𝟏𝟏 𝑭 𝟐𝟐 − 𝑭 𝟏𝟐 𝑭 𝟐𝟏 Thickness evolution
Incompressibility assumption:
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Stress reconstruction
Membrane elastostatics
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Validation
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Deformation gradient Lagrange strain
Aneurismal
aortic tissue Inflation test Optical Full-field measurement ( Full-field displacement)
Inverse procedure
Full-field
Stress reconstruction
Constitutive model
Calculation of stress at rupture
Methodology
S. Avril, P. Badel, A Duprey. Anisotropic and hyperelastic identification of in vitro human arteries from full-field
measurements. Journal of Biomechanics -2010, vol 43, N°15, pp 2978-2985.
J. Kim, S. Avril, A Duprey, JP Favre. Experimental characterization of rupture in human aortic aneurysms using full-field
measurement technique. Biomechanics and Modeling in Mechanobiology, 2012.
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Incompressibility:
J =1
Constitutive model
LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
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Point-wise stress-strain curve fitting
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
RESULTS
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Results
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Local distribution of material
properties
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Statistical analysis of the results
(14) (10)
(24)
(7)
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Ultimate stresses
inflation device
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Rupture modes
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Rupture initiation
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Conclusions
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Modes of rupture???
The tissue thinning starts to localize very early before the rupture
-> presence of aneslatic response in very local areas
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Conclusions
The strength of the tissue is heterogeneous
Existence of weaker zones in the tissue
Damage develops in the weaker zones
Damage leads to rupture when the pressure increases.
What is the microstructural specificity of the weaker zone?
Does it affect the elastic response in the
physiological domain?
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Current questions…
inflation device
Accurate measurement of the thickness distribution
Validity of the incompressibility assumption
Effect of loading conditions and environment
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Future work
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
Microscopic analysis and mcromechanics
Multiphoton-second harmonic generation (MP-SHG) microscope 600x
Intima Media
Smooth muscle cells Elastin fibers
Collagen fibers
Biologic sensor and filter
Adventitia Collagen fibers
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL
In vivo imaging
S. Avril, F. Schneider, C. Boissier, ZY Li. In vivo velocity vector imaging and time-resolved strain rate measurements in the wall of blood vessels using MRI. Journal of Biomechanics, 2010, 44(5) pp 979-983.
US elastography
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LMS Palaiseau - 2013/09/12 - Stéphane AVRIL