title: Viscoelastic characterization of soft tissue from dynamic finite element models.
abstract: An iterative solution to the inverse problem of elasticity and viscosity is proposed in this paper. A new dynamic finite element model that is consistent with known rheological models has been derived to account for the viscoelastic changes in soft tissue. The model assumes known lumped masses at the nodes, and comprises two vectors of elasticity and viscosity parameters that depend on the material elasticity and viscosity distribution, respectively. Using this deformation model and the observed dynamic data for harmonic excitation, the inverse problem is solved to reconstruct the viscosity and elasticity in the medium by using a Gauss-Newton-based approach. As in other inverse problems, previous knowledge of the parameters on the boundaries of the medium is necessary to assure uniqueness and convergence and to obtain an accurate map of the viscoelastic properties. The sensitivity of the solutions to noise, model and boundary conditions has been studied through numerical simulations. Experimental results are also presented. The viscosity and elasticity of a gelatin-based phantom with inclusion of known properties have been reconstructed and have been shown to be close to the values obtained using standard rheometry.
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada. hanie@ece.ubc.ca
authors.forename: Hani
authors.initials: H
authors.lastname: Eskandari
authors.forename: Septimiu E
authors.initials: SE
authors.lastname: Salcudean
authors.forename: Robert
authors.initials: R
authors.lastname: Rohling
authors.forename: Jacques
authors.initials: J
authors.lastname: Ohayon
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D004548:Elasticity; D005780:Gelatin / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008954:Models, Biological; D009928:Organ Specificity; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D014783:Viscosity
chemical_list: D005780:Gelatin