Elasticity Imaging and Sensing using Gas Bubble Dynamics

描述（由申请人提供）：我们项目的总体目标是开发一种基于气泡动力学的成像技术来评估组织的粘弹性特性，并且一般来说，在几种生物医学技术的背景下了解粘弹性介质中的气泡动力学。事实上，微泡在生物医学和临床应用中发挥着越来越重要的作用，微泡不仅在液体中被引入，而且在生物软组织中也被引入。虽然液体中的气泡动力学已经被很好地理解，但组织中气泡的行为却不是。然而，这样的理解可以导致基于气泡在粘弹性介质中的行为以及气泡如何响应内部或外部激励的新型生物医学技术的发展和改进。在目前的项目中，我们将把注意力集中在眼睛组织的激光显微手术上，在那里，激光与组织相互作用产生的气泡被用来切割组织。远程、非侵入性、高时空分辨率、气体微泡行为的实时测量可用于在手术前、手术中和手术后对眼组织的机械特性进行成像或感知。提出了粘弹性介质中气泡动力学的理论、数值和实验研究。我们将建立一个不可压缩弹性介质中气泡径向振荡的非线性模型。所开发的模型将考虑内部气体压力和软组织的复杂性，包括轻微压缩性、组织粘度、组织弹性非均质性和各向异性。我们还将研究被动气泡动力学和气泡在声辐射力等外部激励下的平移运动和振荡。接下来，我们将开发能够测量气泡时空行为的超声波和光学技术。根据这些测量结果，将开发出估计气泡周围组织弹性（杨氏或剪切模量）和粘度的算法。最后，我们将进行实验室研究来验证我们的模型，并展示我们的方法使用气泡动力学成像或感知眼部组织粘弹性的能力。因此，将进行所有的理论和实验研究，以评估所开发的方法在眼科应用中的适用性。

DESCRIPTION (provided by applicant): The overall goal of our program is to develop an imaging technology to assess viscoelastic properties of tissue based on gas bubble dynamics, and, generally, to understand the gas bubble dynamics in viscoelastic medium in the context of several biomedical technologies. Indeed, microbubbles are playing an increasingly important role in biomedical and clinical applications where microbubbles are introduced not only in liquids but also in biological soft tissues. While bubble dynamics in liquid is well understood, the behavior of bubbles in tissue is not. However, such an understanding can lead to the development of novel and improvement of existing biomedical techniques based on how bubbles behave in a viscoelastic medium and how the bubble responds to internal or external excitation. In the current project, we will focus our attention on laser microsurgery of the eye tissue where the bubbles, produced as a result of laser-tissue interaction, are used to cut tissue. The remote, non-invasive, high temporal and spatial resolution, real-time measurements of gas microbubble behavior can be used to image or sense much needed mechanical properties of the eye tissues prior, during and after the surgery. Theoretical, numerical, and experimental studies of gas bubble dynamics in viscoelastic medium are proposed. We will develop a nonlinear model of radial oscillations of a gas bubble in an incompressible elastic medium. The developed model will account for internal gas pressure and the complexity of soft tissue including slight compressibility, tissue viscosity, and tissue elastic heterogeneity and anisotropy. We will also investigate passive bubble dynamics and bubble translational motion and oscillations in response to external excitation such as acoustic radiation force. Next, we will develop ultrasonic and optical techniques capable of measuring the temporal and spatial behavior of the gas bubble. Given these measurements, the algorithms to estimate elasticity (Young's or shear modulus) and viscosity of the tissue surrounding the bubble will be developed. Finally, we will perform laboratory studies to verify our model and to demonstrate the ability of our method to image or sense viscoelasticity of ocular tissues using gas bubble dynamics. Therefore, all theoretical and experimental studies will be conducted to evaluate applicability of the developed methods for ophthalmologic applications.