Post on 03-Jun-2018
8/12/2019 Biomech Applications
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Modelling Biomechanics:applications of the FE method on
nonlinear problems
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Modelling BiomechanicsLinear problems
The finite element method is very commonly used in structural problems, and theoriesof solid mechanics can be used to predict deformation or stresses
Most materials have a linear relationship between stress and strain , for smallenough strains. For hard objects (metals, bone, etc), the theory of linear elasticitysuffices.
8/12/2019 Biomech Applications
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Modelling biomechanics:onlinear stress!strain relationships
"n general the relationship bet#een stress and strain is much more comple$.
%tress is a nonlinear function of strain, but can also depend on the history of theloading & unloading ( hysteresis ). The stress!strain relationship may differ in differentdirections in the material ( isotropic vs anisotropic ) The general theory of nonlinear elasticity has to be used when predictingsoft-tissue deformation
8/12/2019 Biomech Applications
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Modelling biomechanics:stages
Generate mesh ! usually generated using a set of M' images ! images need to segmented before mesh generation
Set up equations to be solved ! time!dependent & static & uasi!static ! stress!strain relationship* nonlinear + #hich form anisotropic ! forces + gravity
Apply appropriate boundary conditions ! usually need to apply a fi$ed displacement boundary condition some#here ! fi$ed or ero e$ternal stress boundary conditions else#here ! can be very difficult to determine appropriate boundary conditions..
umerically compute solution ! develop or use a finite element solver, #hich #ill have to include a nonlinear solver
8/12/2019 Biomech Applications
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Modelling biomechanics:-redicting tumour location in the breast
reast cancer diagnosis is hindered by
the fact that the breast shape variesdramatically bet#een mammographyultrasound and M'".
Mammography: breast is compressed(several directions are possible)MRI: -atient lies on bac/Ultrasound: -atient sits upSurgery (biopsy): -atient lies on bac/
Goal: develop a !" computational modelof the breast from M# images$ whichcan be deformed to simulate otherscenarios and aid diagnosis%
00 ML1
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&redicting tumour location in the breast:mesh generation
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&redicting tumour location in the breast:00 to ML1 mammogram simulation
8/12/2019 Biomech Applications
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&redicting tumour location in the breast:00 to ML1 mammogram simulation
8/12/2019 Biomech Applications
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'ardiac electro-mechanical modelling
Electrical activation of cardiac myocytes induces tension generation + electro!mechanics.
2eformation of cardiac tissue has an influence on electrical activity3hilst a great deal of insight can be gained into cardiac activity & pathology & effect ofdrugs using an electro!physiological tissue model, electro!mechanical models are also ofgreat use
Difficulties in simulating cardiac electro-mechanics:! highly nonlinear (computationally intensive)
! highly anisotropic tissue ! active tension ! residual stress ! suitable boundary conditions
Le4rice et. al., Laminar structure of the heart*
5entricular myocyte arrangement andconnective tissue architecture in the dog, 6778
8/12/2019 Biomech Applications
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'ardiac electro-mechanical modelling
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'ardiac electro-mechanical modelling
8/12/2019 Biomech Applications
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'ardiac electro-mechanical modelling
Model developed at " '"9,%ophia 9ntipolis, France Model developed at Lausanne,%#it erland and Milan, "taly
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'ardiac electro-mechanical modelling
Modelling study + iederer et al., Length-dependent tension in the failing heart and
the efficacy of cardiac resynchroni ation therapy , :;66.0ardiac 'esynchroni ation Therapy (0'T) is a method of treating heart failure thatinvolves implantation of a pacema/er #hich resynchroni es activation!contraction
This study investigated the efficacy of 0'T and suggested a lin/ bet#een 0'T!efficacy and Fran/!%tarling mechanism