The shear wave propagation speed is related to the elasticity and viscosity of the tissue, and can be estimated from phase changes over a short distance traveled. A novel method is proposed to estimate the shear wave ...
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The interaction between microbubble and elastic microvessel wall has been hypothesized to be important in the mechanisms of therapeutic ultrasound applications. In this study, a 2D axisymmetric finite element numerica...
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The interaction between microbubble and elastic microvessel wall has been hypothesized to be important in the mechanisms of therapeutic ultrasound applications. In this study, a 2D axisymmetric finite element numerica...
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ISBN:
(纸本)9781457721762
The interaction between microbubble and elastic microvessel wall has been hypothesized to be important in the mechanisms of therapeutic ultrasound applications. In this study, a 2D axisymmetric finite element numerical model is established to study the interaction between elastic microvessel wall and oscillating microbubble in low frequency ultrasound field using fluid solid interaction method. The numerical results show that the bubble oscillation induces the vessel wall dilation and depression. The maximum von Mises stress of the midpoint on the inner vessel wall could reach 235kPa under PNP 0.2MPa. When the bubble collapses, the von Mises stress is even bigger than that in the expansion phase. The maximum von Mises stress of the midpoint on the inner vessel wall could reach 235kPa under PNP 0.2MPa. When the bubble collapses, the von Mises stress is even bigger than that in the expansion phase. Noticeably, the circumferential stress becomes compressive during collapsing quickly with the magnitude much larger than the maximum tension value. It is possible that the rapid compression stress effect during bubble collapse plays important role in mechanics of microvessel wall endothelial lining disruption due to microbubble cavitation rather than the tensile effect.
When applying the coded transmission technique into the pulsed-echo ultrasound system one of the big problems is the limited time frame for the coding sequence to be feed into the pulse-echo duration. Generally, only ...
When applying the coded transmission technique into the pulsed-echo ultrasound system one of the big problems is the limited time frame for the coding sequence to be feed into the pulse-echo duration. Generally, only very short code sequence could be modulated in each transmitted pulse especially in the medical ultrasound system. Due to the poor correlation property of such kind of short code and the nonlinear field attenuation in the ultrasound propagation, the coding result is far from satisfaction. We have presented a truncated long code scheme for the ultrasound Doppler detection [1] [2]. The time duration to be considered for the selection of the length of the code sequence is extended to be as long as the spectrum estimation window allows. Long code sequence modulation can be applied in the pulse-echo system. The long code is first truncated into many short segments and each segment is used for each pulse modulation. Then, the returned signals from the multiple segments are coherently combined for the Doppler detection. The coding effect with a long code gives a good appearance in the process with its good correlation property, which gives solid backup for the field compensation. Some water tank experiments are shown in this paper.
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