The advent of localization-based super-resolution ultrasound (SRUS) imaging creates a vista for precision vasculature and hemodynamic measurements in brain science, cardiovascular diseases, and cancer. As blinking fluorophores are crucial to super-resolution optical imaging, blinking acoustic contrast agents enabling ultrasound localization microscopy have been highly sought, but only with limited success. Here we report on the discovery and characterization of a type of blinking acoustic nanodroplets (BANDs) ideal for SRUS. BANDs of 200–500 nm diameters comprise a perfluorocarbon-filled core and a shell of DSPC, Pluronic F68, and DSPE-PEG2000. When driven by clinically safe acoustic pulses (MI < 1.9) provided by a diagnostic ultrasound transducer, BANDs underwent reversible vaporization and reliquefaction, manifesting as “blinks”, at rates of up to 5 kHz. By sparse activation of perfluorohexane-filled BANDs-C₆ at high concentrations, only 100 frames of ultrasound imaging were sufficient to reconstruct super-resolution images of a no-flow tube through either cumulative localization or temporal radiality autocorrelation. Furthermore, the use of high-density BANDs-C_6–4 (1 × 10⁸/mL) with a 1:9 admixture of perfluorohexane and perfluorobutane supported the fast SRUS imaging of muscle vasculature in live animals, at 64 μm resolution requiring only 100 frames per layer. We anticipate that the BANDs developed here will greatly boost the application of SRUS in both basic science and clinical settings.

中文翻译：

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闪烁的声学纳米液滴使快速超分辨率超声成像成为可能

基于定位的超分辨率超声 (SRUS) 成像的出现为脑科学、心血管疾病和癌症中的精确脉管系统和血流动力学测量创造了前景。由于闪烁荧光团对超分辨率光学成像至关重要，因此人们一直在寻求能够实现超声定位显微镜的闪烁声学造影剂，但成功率有限。在这里，我们报告了一种非常适合 SRUS 的闪烁声学纳米液滴 (BAND) 的发现和表征。直径为 200-500 nm 的 BAND 包含一个全氟化碳填充的核和一个 DSPC、Pluronic F68 和 DSPE-PEG2000 的壳。当由诊断超声换能器提供的临床安全声脉冲 (MI < 1.9) 驱动时，BANDs 经历可逆汽化和再液化，表现为“闪烁”，速率高达 5 kHz。通过全氟己烷填充 BANDs-C 的稀疏激活₆在高浓度下，仅 100 帧超声成像就足以通过累积定位或时间径向自相关重建无流量管的超分辨率图像。此外，使用具有 1:9 全氟己烷和全氟丁烷混合物的高密度 BANDs-C _6–4 (1 × 10 ⁸ /mL) 支持活体动物肌肉血管系统的快速 SRUS 成像，分辨率为 64 μm，仅需要每层 100 帧。我们预计这里开发的 BAND 将极大地促进 SRUS 在基础科学和临床环境中的应用。