Zhang Ge, Harput Sevan, Hu Hanyu, Christensen-Jeffries Kirsten, Zhu Jiaqi, Brown Jemma, Leow Chee Hau, Eckersley Robert J, Dunsby Christopher, Tang Meng-Xing
IEEE Trans Ultrason Ferroelectr Freq Control. 2019 Mar 25. doi: 10.1109/TUFFC.2019.2906496.
Localization-based ultrasound super-resolution imaging using microbubble contrast agents and phase-change nano-droplets has been developed to visualize microvascular structures beyond the diffraction limit. However, the long data acquisition time makes the clinical translation more challenging. In this study, fast acoustic wave sparsely activated localization microscopy (fast-AWSALM) was developed to achieve super-resolved frames with sub-second temporal resolution, by using low-boiling-point octafluoropropane nanodroplets and high frame rate plane waves for activation, destruction, as well as imaging. Fast-AWSALM was demonstrated on an in vitro microvascular phantom to super-resolve structures that could not be resolved by conventional B-mode imaging. The effects of the temperature and mechanical index on fast-AWSALM was investigated. Experimental results show that sub-wavelength micro-structures as small as 190 lm were resolvable in 200 ms with plane-wave transmission at a center frequency of 3.5 MHz and a pulse repetition frequency of 5000 Hz. This is about a 3.5 fold reduction in point spread function full-width-half-maximum compared to that measured in conventional B-mode, and two orders of magnitude faster than the recently reported AWSALM under a non-flow/very slow flow situations and other localization based methods. Just as in AWSALM, fast-AWSALM does not require flow, as is required by current microbubble based ultrasound super resolution techniques. In conclusion, this study shows the promise of fast-AWSALM, a super-resolution ultrasound technique using nanodroplets, which can generate super-resolution images in milli-seconds and does not require flow.
利用微泡造影剂和相变纳米液滴的基于定位的超声超分辨率成像技术已被开发出来，用于可视化超出衍射极限的微血管结构。然而，较长的数据采集时间使得其临床转化更具挑战性。在本研究中，通过使用低沸点八氟丙烷纳米液滴和高帧率平面波进行激活、破坏以及成像，开发了快速声波稀疏激活定位显微镜（fast-AWSALM），以实现具有亚秒级时间分辨率的超分辨帧。在体外微血管模型上对fast-AWSALM进行了演示，以超分辨传统B模式成像无法分辨的结构。研究了温度和机械指数对fast-AWSALM的影响。实验结果表明，在中心频率为3.5 MHz、脉冲重复频率为5000 Hz的平面波传输条件下，在200 ms内可分辨小至190 lm的亚波长微结构。与传统B模式测量的点扩散函数半高宽相比，这大约降低了3.5倍，并且比最近报道的在非流动/非常缓慢流动情况下的AWSALM和其他基于定位的方法快两个数量级。与AWSALM一样，fast-AWSALM不需要流动，而目前基于微泡的超声超分辨率技术需要流动。总之，本研究展示了fast-AWSALM的前景，这是一种使用纳米液滴的超分辨率超声技术，它可以在毫秒内生成超分辨率图像，并且不需要流动。
