title: Extension of the Optimized Virtual Fields Method to estimate viscoelastic material parameters from 3D dynamic displacement fields.
abstract: In-vivo measurement of the mechanical properties of soft tissues is essential to provide necessary data in biomechanics and medicine (early cancer diagnosis, study of traumatic brain injuries,etc.). Imaging techniques such as Magnetic Resonance Elastography (MRE) can provide 3D displacement maps in the bulk and in vivo, from which, using inverse methods, it is then possible to identify some mechanical parameters of the tissues (stiffness, damping etc.). The main difficulties in these inverse identification procedures consist in dealing with the pressure waves contained in the data and with the experimental noise perturbing the spatial derivatives required during the processing. TheOptimizedVirtual Fields Method (OVFM) [1], designed to be robust to noise, present natural and rigorous solution to deal with these problems. The OVFM has been adapted to identify material parameter maps from Magnetic Resonance Elastography (MRE) data consisting of 3-dimensional displacement fields in harmonically loaded soft materials. In this work, the method has been developed to identify elastic and viscoelastic models. The OVFM sensitivity to spatial resolution and to noise has been studied by analyzing 3D analytically simulated displacement data. This study evaluates and describes the OVFM identification performances: different biases on the identified parameters are induced by the spatial resolution and experimental noise. The well-known identification problems in the case of quasi-incompressible materials also find a natural solution in the OVFM. Moreover, ana posterioricriterion to estimate the local identification quality is proposed. The identification results obtained on actual experiments are briefly presented.
authors.affiliation: Laboratoire TIMC-IMAG, Université de Grenoble (INPG-UJF), BP 53, 38041 Grenoble Cedex 9, France.
authors.forename: N
authors.initials: N
authors.lastname: Connesson
authors.affiliation: Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, One Brookings Drive, Campus Box 1185, St. Louis, Missouri 63130, USA.
authors.forename: E H
authors.initials: EH
authors.lastname: Clayton
authors.affiliation: Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, One Brookings Drive, Campus Box 1185, St. Louis, Missouri 63130, USA.
authors.forename: P V
authors.initials: PV
authors.lastname: Bayly
authors.affiliation: Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: F
authors.initials: F
authors.lastname: Pierron
keywords: MR elastography; elasticity; elasticity reconstruction; inverse problem; noise robustness; noise sensitivity; optimized virtual fields; virtual fields method; viscoelasticity