利用声控可切换纳米液滴实现体内快速选择性超分辨超声成像
Fast and selective super-resolution ultrasound in vivo with sono-switchable nanodroplets
AI总结：
本文提出 AWSALM 与 fast-AWSALM，利用声控可切换纳米液滴实现按需、高浓度、快速选择性的体内超分辨超声微血管成像。
摘要：
微循环灌注是组织发育、维持和病理变化的关键。因此，以高时空分辨率测量灌注具有重要价值，但在深部组织中仍是一项挑战。超声定位显微镜（ULM）可提供极高的时空分辨率，但使用微泡需要较低的造影剂浓度、较长的采集时间，并且对微泡的时空分布几乎无法控制。本研究首次展示了用于体内超分辨超声成像的声波稀疏激活定位显微镜（AWSALM）和快速 AWSALM，可提供按需造影和血管选择性。研究测试了三种不同配方的声控可切换造影剂。我们证明，在远低于推荐安全限值的超声机械指数下即可使用这些试剂，从而在极高试剂浓度下实现快速的按需稀疏切换。我们生成了兔肾血管系统的超定位图谱，采集时间介于5.5秒至0.25秒之间，空间分辨率提高了4倍。我们展示了 AWSALM 在显示特定血管分支和下游微血管方面的独特选择性，并通过快速 AWSALM 显示了收缩期和舒张期的超定位肾脏结构。总之，我们证明了利用超声和声控可切换纳米液滴，以亚波长分辨率在体内快速、选择性测量微血管动力学的可行性。
英文摘要：
Perfusion by the microcirculation is key to the development, maintenance and pathology of tissue. Its measurement with high spatiotemporal resolution is consequently valuable but remains a challenge in deep tissue. Ultrasound Localization Microscopy (ULM) provides very high spatiotemporal resolution but the use of microbubbles requires low contrast agent concentrations, a long acquisition time, and gives little control over the spatial and temporal distribution of the bubbles. The present study is the first to demonstrate Acoustic Wave Sparsely-Activated Localization Microscopy (AWSALM) and fast-AWSALM for in vivo super-resolution ultrasound imaging, offering contrast on demand and vascular selectivity. Three different formulations of sono-switchable contrast agents were tested. We demonstrate their use with ultrasound mechanical indices well within recommended safety limits to enable fast on-demand sparse switching at very high agent concentrations. We produce super-localization maps of the rabbit renal vasculature with acquisition times between 5.5 s and 0.25 s, and an 4-fold improvement in spatial resolution. We present the unique selectivity of AWSALM in visualizing specific vascular branches and downstream microvasculature, and we show super-localized kidney structures in systole and diastole with fast-AWSALM. In conclusion we demonstrate the feasibility of fast and selective measurement of microvascular dynamics in vivo with subwavelength resolution using ultrasound and sono-switchable nanodroplets.
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