Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
Ultrason Sonochem. 2024 Oct;109:106984. doi: 10.1016/j.ultsonch.2024.106984. Epub 2024 Jul 11.
Acoustic droplet vaporization (ADV) offers a dynamic approach for generating bubbles on demand, presenting new possibilities in biomedical applications. Although ADV has been investigated in various biomedical applications, its potential in tissue characterization remains unexplored. Here, we investigated the effects of surrounding media on the radial dynamics and acoustic emissions of ADV bubbles using theoretical and experimental methodologies. For theoretical studies, bubble dynamics were combined with the Kelvin-Voigt material constitutive model, accounting for viscoelasticity of the media. The radial dynamics and acoustic emissions of the ADV-bubbles were recorded via ultra-high-speed microscopy and passive cavitation detection, respectively. Perfluoropentane phase-shift droplets were embedded in tissue-mimicking hydrogels of varying fibrin concentrations, representing different elastic moduli. Radial dynamics and the acoustic emissions, both temporal and spectral, of the ADV-bubbles depended significantly on fibrin elastic modulus. For example, an increase in fibrin elastic modulus from ≈0.2 kPa to ≈6 kPa reduced the maximum expansion radius of the ADV-bubbles by 50%. A similar increase in the elastic modulus significantly impacted both linear (e.g., fundamental) and nonlinear (e.g., subharmonic) acoustic responses of the ADV-bubbles, by up to 10 dB. The sensitivity of ADV to the surrounding media was dependent on acoustic parameters such as driving pressure and the droplets concentration. Further analysis of the acoustic emissions revealed distinct ADV signal characteristics, which were significantly influenced by the surrounding media.
声致空化（ADV）提供了一种按需产生气泡的动态方法，为生物医学应用带来了新的可能性。尽管 ADV 已经在各种生物医学应用中进行了研究，但它在组织特征化方面的潜力尚未得到探索。在这里，我们使用理论和实验方法研究了周围介质对 ADV 气泡的径向动力学和声发射的影响。对于理论研究，将气泡动力学与 Kelvin-Voigt 材料本构模型相结合，考虑了介质的粘弹性。通过超高速显微镜和被动空化检测分别记录 ADV 气泡的径向动力学和声发射。全氟戊烷相移液滴嵌入不同纤维蛋白浓度的组织模拟水凝胶中，代表不同的弹性模量。ADV 气泡的径向动力学和声发射（包括时间和光谱）都显著依赖于纤维蛋白弹性模量。例如，纤维蛋白弹性模量从约 0.2 kPa 增加到约 6 kPa，会使 ADV 气泡的最大膨胀半径减小 50%。类似地，弹性模量的显著增加会显著影响 ADV 气泡的线性（例如，基频）和非线性（例如，次谐波）声响应，幅度高达 10 dB。ADV 对周围介质的敏感性取决于声参数，如驱动压力和液滴浓度。对声发射的进一步分析揭示了 ADV 信号的独特特征，这些特征受到周围介质的显著影响。
