11C-5 Characterization of Time-Varying Mechanical Viscoelastic Parameters of Mimicking Deep Vein Thrombi with 2D Dynamic Elastography

Staging mechanical properties of deep vein thrombi (elasticity and viscosity) can be of importance for therapy planning because the compactness of a blood clot impacts the efficiency of thrombolysis drugs. This article proposes the dynamic vascular elastography (DVE) method to solve this problem. It consists to retrieve viscoelastic parameters of 8-mm diameter blood clot cylindrical inclusions from shear wave propagation characteristics. The technique firstly implies the generation of a low frequency (50-190 Hz) harmonic plane shear wave in the medium and the tracking of this wave with an ultra- fast ultrasound scanner (frame rate > 3000 Hz). An inverse problem was formulated as a least-square minimization between simulations and experimental results of viscoelasticity. The wave excitation technique also permitted to do a multi-frequency analysis to validate the Voigt´s model as a valid approach to represent the viscoelasticity of blood clots. DVE proved to have sufficient sensitivity to follow the time-varying blood coagulation process and to differentiate mechanical properties of blood samples with different hematocrits.