Correspondence of ultrasound elasticity imaging to direct mechanical measurement in aging DVT in rats

Abstract

Previous ultrasound elasticity imaging experiments supported a generally accepted concept that the hardness of deep venous thrombi increases with thrombus aging. Results also showed that this noninvasive imaging technique can accurately predict thrombus age through strain estimates in a well controlled animal study. In the present study, as an alternative means to characterize elastic properties of thrombi, we employed a direct mechanical measurement system to estimate Young's modulus of ex vivo thrombi. Unlike conventional indentation tests, the device utilizes a specific compression geometry for cylindrical tissue specimens. We also proposed an approximation scheme to retrieve Young's modulus from force-displacement measurements made using the device. Finite element simulations and calibrations on tissue-mimicking phantoms validated the system. Then, using two groups of rats with surgically induced thrombi, we further investigated the correlation between Young's modulus measured ex vivo and elasticity images reconstructed in vivo. This comparison was accomplished by converting the intra-thrombus strains measured in the in vivo studies into Young's modulus estimates using a model based approach. Good agreement between time-dependent Young's modulus estimates observed in vivo and direct measurements of Young's modulus using the mechanical device helps to confirm the ability of elasticity imaging to age DVT for efficient treatment.

Medical ultrasound: imaging of soft tissue strain and elasticity

“…If the clot is acute, the patient should be given intravenous heparin to disperse it, followed by oral anticoagulant; but if the clot is chronic, only oral anticoagulant should be prescribed. Using a rat model, good correlation has been demonstrated between the age-related Young's modulus of thrombus determined by ultrasonic elastography and that subsequently directly measured ex vivo [28]. This suggests that ultrasonic thrombus elastography might be used to select the appropriate therapy for patients with deep vein thrombosis.…”

Measurement of the Dynamic Shear Modulus of Mouse Brain Tissue In Vivo by Magnetic Resonance Elastography

“…The expression for displacement can be simplified to , where C is a coefficient of proportionality. Since the gradients are applied in one direction at a time the coefficient of proportionality in the i th direction is (2) where G o,i is the gradient amplitude in the i th direction.…”

“…Changes in material stiffness can indicate the presence of tumors and other diseases [1]. In the case of deep venous thrombosis (DVT), hardness of the thrombus is closely related to thrombus maturity, which in turn determines the appropriate course of treatment [2]. Physicians have long relied on hand palpation to detect the presence of a tumor where other imaging methods such as ultrasound, CT, and MRI have failed to do so.…”

Large deforming buoyant embolus passing through a stenotic common carotid artery: A computational simulation

“…A large strain formulation was used with the rubber/foam material model, named as Sussman-Bathe (Sussman and Bathe, 2009). In this paper, measured stress-strain curve obtained from ultrasound elasticity imaging of a 3-day-old thrombus (Xie et al, 2005) was set precisely to the Sussman-Bathe model as it is shown in Fig. 2.…”