Elasticity Imaging and Sensing using Gas Bubble Dynamics

描述(申请人提供)：我们项目的总体目标是开发一种成像技术，以基于气泡动力学来评估组织的粘弹性属性，并总体上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，其中微泡不仅被引入液体中，而且被引入生物软组织中。虽然液体中的气泡动力学已经很好地了解了，但组织中气泡的行为还不是很清楚。然而，这样的理解可以导致新的生物医学技术的发展和现有生物医学技术的改进，这些技术基于气泡在粘弹性介质中的行为以及气泡对内部或外部激励的响应。在目前的项目中，我们将重点关注眼组织的激光显微手术，其中由于激光与组织相互作用而产生的气泡被用来切割组织。对气体微泡行为的远程、非侵入性、高时间和空间分辨率的实时测量可用于成像或感知手术前、手术中和手术后眼部组织急需的机械特性。对粘弹性介质中气泡动力学进行了理论、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动的非线性模型。所开发的模型将考虑内部气体压力和软组织的复杂性，包括轻微的可压缩性、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以及气泡在外部激励(如声辐射力)下的平移运动和振荡。接下来，我们将开发能够测量气泡的时间和空间行为的超声波和光学技术。根据这些测量结果，将开发出估算气泡周围组织的弹性(杨氏或剪切弹性)和粘性的算法。最后，我们将进行实验室研究来验证我们的模型，并证明我们的方法能够使用气泡动力学来成像或感测眼组织的粘弹性。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.