Acoustic Contrast Agents for Use with High-frequency Ultrasound

描述（由申请人提供）：本研究的目的是利用声学造影剂和高频超声（HFU，> 10 MHz）对微循环成像并通过声孔作用启动基因转染。目前的造影剂不是为这些高频率设计的。该研究将评估两个重要的应用：1）兔眼和小鼠胚胎中慢流微血管的成像; 2）小鼠胚胎中声穿孔的启动，以评估基因转染的潜力。与常规成像频率（< 10 MHz）不同，HFU提供了实现微循环成像精细尺度横向分辨率和声孔作用高度局部化压力暴露的方法。具体来说，我们建议进行全面的理论和实验研究有关的高频超声激发声学造影剂。目前可用的蛋白质、脂质和聚合物壳的试剂沿着以及我们自己定制的聚合物壳的试剂将通过实验表征以量化反向散射（散射截面、非线性响应等），衰减、声速和破坏阈值。将开发扩展有充分根据的早期模型的理论模型，并将径向响应和代理破坏的模拟与实验结果进行比较。这些模型将用于更好地了解造影剂的最佳材料特性，用于HFU应用，并深入了解导致造影剂破坏的物理机制。然后，理论和实验结果将用于制定成像和信号处理策略，以更好地可视化微循环。从最初的实验和理论工作中获得的知识也将被应用于优化体内动物实验的声学暴露条件。造影剂将用于兔眼和小鼠胚胎中的微循环成像，以及通过小鼠胚胎中的声孔作用启动基因转染。动物实验，特别是那些涉及兔眼的实验，将与人类疾病的成像直接相关，包括青光眼（美国有2-3百万），黄斑变性（美国每年有200，000例新发病例），和原发性眼内肿瘤（美国每年有3，000例新发病例）。例如，使用造影剂的HFU可能有助于诊断青光眼，青光眼是美国失明的主要原因，通过允许评估视神经和睫状体中的微循环。公共卫生相关性本研究的最终目标是将声学造影剂的使用扩展到更高的频率，以允许微循环成像和通过声孔作用启动基因转染。我们产生的知识将有助于设计新的药物，优化声学暴露条件，并最终导致新的临床应用，如眼科疾病诊断和靶向基因转染。

DESCRIPTION (provided by applicant): The goal of this study is to utilize acoustic contrast agents with high-frequency ultrasound (HFU, > 10 MHz) in order to image microcirculation and initiate gene transfection via sonoporation. Current contrast agents were not designed for these high frequencies. The study will assess two important applications: 1) imaging of slow-flow microvasculature in rabbit eyes and mouse embryos; and 2) the initiation of sonoporation in mouse embryos to assess the potential for gene transfection. Unlike with conventional imaging frequencies (< 10 MHz), HFU provides the means to achieve fine-scale lateral resolution for microcirculation imaging and highly localized pressure exposure for sonoporation. Specifically, we propose undertaking comprehensive theoretical and experimental studies related to HFU excitation of acoustic contrast agents. Currently available protein-, lipid-, and polymer-shelled agents along with our own custom-made, polymer-shelled agents will be characterized experimentally to quantify backscatter (scattering cross section, nonlinear response, etc.), attenuation, speed of sound, and destruction threshold. Theoretical models that extend well-founded earlier models will be developed and simulations of radial response and agent destruction will be compared to experimental results. The models will be utilized to better understand the optimal material properties of contrast agents for HFU applications and to gain insight into the physical mechanisms that lead to the destruction of contrast agents. The theoretical and experimental results will then be used to formulate imaging and signal processing strategies to better visualize microcirculation. Knowledge gained from the initial experimental and theoretical work will also be applied to optimizing acoustic exposure conditions for in vivo animal experiments. The contrast agents will be used to image microcirculation in rabbit eyes and mouse embryos as well as to initiate gene transfection via sonoporation in mouse embryos. The animal experiments, particularly those involving the rabbit eye, will have direct relevance for imaging human diseases including glaucoma (2-3 million in U.S.), macular degeneration (200,000 new cases each year in U.S.), and primary intraocular tumors (3,000 new cases each year in U.S.). For instance, HFU with contrast agents may help diagnose glaucoma, the leading cause of blindness in the U.S., by permitting the assessment of microcirculation in the optic nerve and ciliary body. PUBLIC HEALTH RELEVANCE The ultimate goal of this research is to extend the use of acoustic contrast agents to higher frequencies in order to permit the imaging of microcirculation and the initiation of gene transfection via sonoporation. The knowledge we generate will assist in the design of new agents, optimizing acoustic exposure conditions, and, ultimately, will lead to new clinical applications such as ocular disease diagnosis and targeted gene transfection.