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高频超声（HFU, > 10 MHz）的声学造影剂，通过超声穿孔成像微循环并启动基因转染。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)兔眼和小鼠胚胎慢流微血管成像；2)在小鼠胚胎中启动超声，以评估基因转染的潜力。与传统成像频率（< 10 MHz）不同，HFU提供了实现微循环成像的精细尺度横向分辨率和超声成像的高度局部压力曝光的手段。具体而言，我们建议对声学造影剂的HFU激发进行全面的理论和实验研究。目前可用的蛋白质、脂质和聚合物壳剂以及我们自己定制的聚合物壳剂将进行实验表征，以量化后向散射（散射截面、非线性响应等）、衰减、声速和破坏阈值。将发展理论模型，扩展建立良好的早期模型，并将径向响应和剂破坏的模拟与实验结果进行比较。这些模型将被用来更好地理解用于HFU应用的造影剂的最佳材料特性，并深入了解导致造影剂破坏的物理机制。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应用于优化动物体内实验的声暴露条件。造影剂将用于兔眼和小鼠胚胎的微循环成像，以及通过超声穿孔在小鼠胚胎中启动基因转染。动物实验，特别是兔眼实验，将与人类疾病成像直接相关，包括青光眼（美国200 - 300万例）、黄斑变性（美国每年新发病例20万例）和原发性眼内肿瘤（美国每年新发病例3000例）。例如，使用造影剂的HFU可以通过评估视神经和睫状体的微循环来帮助诊断青光眼，青光眼是美国致盲的主要原因。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，以便通过超声穿孔进行微循环成像和基因转染的启动。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，并最终将导致新的临床应用，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.