CAREER: Evaluating the distribution of bubble nuclei for acoustic cavitation in tissues

超声应用中的一个主要问题，如胎儿成像，是声空化（超声场中气泡的产生、振荡和破裂），因为气泡会损害组织。在临床超声成像中，通过要求机器显示机械指数来降低风险，机械指数是测量空化可能性的一种方法。然而，超声的治疗应用是利用声空化来破坏肾结石或破坏癌组织。声空化是由气泡成核引起的，但没有人知道人体组织中的气泡核是由什么构成的，以及这些气泡核是如何受到组织中沉积矿物质的某些疾病的影响的。因此，该项目的总体目标是了解健康组织中泡核的构成，并开发超声来灵敏地检测矿物质沉积在组织中时泡核的变化。这项研究将为开发一种互动课堂活动工具包提供基础，该工具包专门用于提高儿童的科学兴趣和素养，以及教育所有学科的研究生进行科学交流和推广，从而增加这项工作的社会影响，而不是一个科学家或实验室自己可以做到的。研究者的长期职业目标是成为生物组织中气泡成核和声空化的领导者。为了实现这一目标，本CAREER项目的目标是通过确定声空化组织中气泡核的位置来提高超声诊断和治疗的安全性。采用实验和建模相结合的方法，研究计划分为三个目标。第一个目的是评估具有不同疏水性和力学特性的健康生物结构（大鼠骨骼肌、肝细胞和乳腺细胞）中可经历声空化的泡核的分布。研究旨在验证声空化将主要发生在细胞外的假设，在机械可延展性的细胞外基质中，声空化会增加。预期结果包括：1)在二维和三维细胞培养中，泡核主要存在于细胞内还是细胞外；2)评价胶原凝胶和脱细胞细胞外基质的力学性能对泡核分布的影响；3)基于气泡动力学和破裂模型的改进空化可能性度量。第二个目的是确定生物矿化对动脉粥样硬化（胆固醇结晶）、痛风（尿酸结晶）、异位骨化（磷酸钙）和乳房微钙化（草酸钙）等疾病的泡核分布的影响。研究的目的是验证这样一个假设，即所有形式的病理性生物矿化都将有稳定的缝隙微泡隔离在矿物表面。预期的结果包括：1)了解气泡核在实验室生长晶体上的分布；2)评价了表面张力对实验室生长晶体中气泡核分布的影响；3)确定病理性生物矿化过程中细胞沉积的矿物质如何影响泡核的分布。第三个目标是开发彩色多普勒超声闪烁伪影，用于声空化对矿物沉积的灵敏检测。前两个目标中健康组织和矿化组织中的泡核分布将被用来改善彩色多普勒超声闪烁伪影，用于检测所有形式的矿化，包括痛风、动脉粥样硬化、异位骨化、乳房微钙化和肾结石。研究旨在验证晶体组成和周围环境将影响多普勒成像方案以最佳检测每种形式的病理性生物矿化的假设。预期结果包括：1)多普勒成像协议，以增强对每种已确定的病理性生物矿化形式的闪烁；2)从原始多普勒超声信号预测晶体组成。这项基础研究的结果将提供所有形式的病理性生物矿化之间的第一个联系-即矿化发生后存在稳定的缝隙微泡，甚至可能导致细胞恢复到病变或矿物沉积状态。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A major concern in every ultrasound application, such as fetal imaging, is acoustic cavitation (the creation, oscillation, and collapse of bubbles in an ultrasound field) because bubbles can damage tissues. In clinical ultrasound imagers, the risk is lessoned by requiring machines to display the mechanical index, which is a measure of the likelihood of cavitation. Yet therapeutic applications of ultrasound make use of acoustic cavitation to break kidney stones or destroy cancerous tissues. Acoustic cavitation arises from nucleation of bubbles, but no one understands what constitutes a bubble nucleus in human tissues and how these bubble nuclei might be influenced by certain diseases that deposit minerals in tissues. Thus, the overall goals of the project are to understand what constitutes a bubble nucleus in healthy tissues and to develop ultrasound to sensitively detect changes in bubble nuclei that occur when minerals are deposited in tissues. This research will provide a basis for developing an interactive classroom activity kit specifically designed to enhance the scientific interest and literacy of children, as well as educate graduate students from all disciplines on scientific communication and outreach, thereby increasing the societal impact of this work beyond what one scientist or lab can do on their own.The Investigator’s long-term career goal is to become a leader in bubble nucleation and acoustic cavitation in biological tissues. Toward this goal, the goal of this CAREER project is to improve the safety of diagnostic and therapeutic ultrasound by determining where bubble nuclei exist in tissues for acoustic cavitation. Using a combination of experimentation and modeling, the Research Plan is organized under three objectives. The FIRST Objective is to evaluate the distribution of bubble nuclei that can undergo acoustic cavitation in healthy biological structures (rat skeletal muscle, hepatocyte, and mammary cells) with varying hydrophobicity and mechanical properties. Studies are designed to test the hypothesis that acoustic cavitation will occur predominantly extracellularly, with increased acoustic cavitation occurring in a mechanically malleable extracellular matrix. Expected results include: 1) identification of whether bubble nuclei exist predominantly intracellularly or extracellularly in 2D and 3D cell culture; 2) evaluation of the effects of mechanical properties in collagen gels and decellularized extracellular matrix on the distribution of bubble nuclei; and 3) an improved metric for the likelihood of cavitation based on a bubble dynamics and fracture model. The SECOND Objective is to determine the effect of biomineralization on the distribution of bubble nuclei for diseases including atherosclerosis (cholesterol crystals), gout (uric acid crystals), heterotopic ossification (calcium phosphate) and breast microcalcifications (calcium oxalate). Studies are designed to test the hypothesis that all forms of pathological biomineralization will have stabilized crevice microbubbles isolated to the surface of the minerals. Expected results include: 1) an understanding of the distribution of bubble nuclei on lab-grown crystals; 2) an evaluation of the effects of surface tension on the distribution of bubble nuclei in lab-grown crystals; and 3) a determination of how the mineral deposition by cells in pathological biomineralization influence the distribution of bubble nuclei. The THIRD Objective is to develop the color Doppler ultrasound twinkling artifact for sensitive detection of mineral deposition through acoustic cavitation. The distribution of bubble nuclei in healthy and mineralized tissues from the first two objectives will be leveraged to improve the color Doppler ultrasound twinkling artifact for detection of all forms of mineralization including gout, atherosclerosis, heterotopic ossifications, breast microcalcifications and kidney stones. Studies are designed to test the hypothesis that crystal composition and the surrounding environment will influence the Doppler imaging protocols for optimal detection of each form of pathological biomineralization. Expected results include: 1) Doppler imaging protocols to enhance twinkling specific to each identified form of pathological biomineralization and 2) prediction of the crystal composition from the raw Doppler ultrasound signals. The results from this fundamental research will provide the first connection between all forms of pathological biomineralization – namely that stabilized crevice microbubbles are present after mineralization occurs and may even cause cells to revert to the diseased or mineral-depositing state.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.