背景:结合溶栓药物和/或微泡,超声(US)已被认为是溶栓治疗的一个有用的工具,利用其非侵入性的优势,非电离,低成本,以及对身体深处组织的精确定位。最近,低强度脉冲美国,除了更剧烈的影响之外,通过稳定的空化和声流可以减少并发症,引起了广泛的关注。
目标:然而,由于皮肤和目标血管之间没有理想的平行多层结构,因此实践中的溶栓效果可能达不到预期.因此,目前的工作旨在更好地阐明US入射角对产生声流和溶栓效果的影响。
方法:系统的数值和实验研究,即,有限元建模(FEM),粒子图像测速(PIV),和体外溶栓测量,进行了估计声/流场模式,最大流速,和血栓表面的剪切应力,以及在不同条件下产生的裂解速率。这些方法旨在验证以下假设:流诱导的涡流可以进一步加速血栓的溶解,并且可以通过调整US入射角来实现优化的溶栓效果。
结果:池数据结果表明,从FEM模拟和PIV实验获得的流速和剪切应力的变化趋势在质量上彼此一致。存在一个最佳的入射角,可以最大限度地提高血栓表面的流速和剪切应力。从而可以产生优异的搅拌和混合效果。此外,由于血栓表面的流速和剪切应力均与溶栓效果高度相关(相关系数R1=0.988,R2=0.958),裂解率的峰值(增加至少5.02%)也出现在10°。
结论:目前的结果表明,具有适当确定的入射角,可以在不增加驱动压力的情况下实现更高的溶栓率。它可能会阐明美国未来的溶栓计划策略,如果与其他先进技术结合使用(例如,基于机器学习的图像分析和图像引导的自适应美国发射调制),可以实现更有效的溶栓效果,同时最大限度地减少由过高压力引起的不良副作用。
BACKGROUND: Combined with thrombolytic drugs and/or microbubbles, ultrasound (US) has been regarded as a useful tool for thrombolysis treatment by taking its advantages of noninvasive, non-ionization, low cost, and accurate targeting of tissues deep in body. Recently, low-intensity pulsed US, which can cause fewer complications by stable cavitation and acoustic streaming other than more violent effects, has attracted broad attention.
OBJECTIVE: However, the thrombolysis effect in practice might not achieve expectation because there is not an ideal parallel multilayered structure between the skin and the targeted vessel. Therefore, the current work aims to better elucidate the influence of US incident angle on the generation of acoustic streaming and thrombolysis effect.
METHODS: Systemic numerical and experimental studies, namely, finite element modeling (FEM), particle image velocimetry (PIV), and in vitro thrombolysis measurements, were performed to estimate the acoustical/streaming field pattern, maximum flow velocity, and shear stress on the surface of thrombus, as well as the lysis rate generated at different conditions. These methods aim at verifying the hypothesis that streaming-induced vortices can further accelerate the dissolution of the thrombus and optimized thrombolysis effected can be achieved by adjusting US incident angles.
RESULTS: The pool data results showed that the variation trends of the flow velocity and shear stress obtained from FEM simulation and PIV experiments are qualitatively consistent with each other. There exists an optimal incident angle that can maximize the flow velocity and shear stress on the surface of thrombus, so that superior stirring and mixing effect can be generated. Furthermore, as the flow velocity and shear stress on thrombus surface are both highly correlated with the thrombolysis effect (the correlation coefficient R1 = 0.988, R2 = 0.958, respectively), the peak value of lysis rate (increase by at least 5.02%) also occurred at 10°.
CONCLUSIONS: The current results demonstrated that, with appropriately determined incident angle, higher thrombolysis rate could be achieved without increasing the driving pressure. It may shed the light on future US thrombolysis planning strategy that, if combined with other advanced technologies (e.g., machine-learning-based image analysis and image-guided adaptive US emission modulation), more efficient thrombolytic effect could be realized while minimizing undesired side-effects caused by excessively high pressure.