Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high-speed optical microscopy.
Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high-speed optical microscopy.
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DOI：
10.1088/0031-9155/58/13/4513
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发表时间：
2013-07-07
影响因子：
3.5
通讯作者：
Dayton PA
中科院分区：
文献类型：
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作者：
Sheeran PS;Matsunaga TO;Dayton PA
基于全氟化碳液滴的超声激活相变造影剂（PCCA）已被提议用于各种治疗和诊断临床应用。当以纳米级产生时，液滴可能小到足以离开血管空间，然后通过外部施加的超声波以高空间和时间特异性诱导汽化。由于较大异常液滴的影响，使用声学技术来优化给定应用的超声参数对于纳米级 PCCA 来说可能是一个重大挑战。同样，由于纳米液滴剂的亚微米尺寸和光学显微镜的分辨率限制，光学技术可能是一个挑战。在这项研究中，评估了一种光学方法，用于确定纳米级乳液的活化阈值，该方法基于单次短（<10 个周期）超声脉冲后 PCCA 蒸发产生的气泡的体外分布。通过超高速显微镜观察发现，蒸发液滴在脉冲早期产生的气泡受到随后的蒸发脉冲周期的强烈影响，并且这些影响随着脉冲长度的增加而增加。结果表明，峰值直径约为 200 nm 的十氟丁烷纳米乳液可以使用适合临床诊断超声机的压力通过短脉冲实现最佳汽化。
Ultrasonically activated phase-change contrast agents (PCCAs) based on perfluorocarbon droplets have been proposed for a variety of therapeutic and diagnostic clinical applications. When generated at the nanoscale, droplets may be small enough to exit the vascular space and then be induced to vaporize with high spatial and temporal specificity by externally-applied ultrasound. The use of acoustical techniques for optimizing ultrasound parameters for given applications can be a significant challenge for nanoscale PCCAs due to the contributions of larger outlier droplets. Similarly, optical techniques can be a challenge due to the sub-micron size of nanodroplet agents and resolution limits of optical microscopy. In this study, an optical method for determining activation thresholds of nanoscale emulsions based on the in vitro distribution of bubbles resulting from vaporization of PCCAs after single, short (<10 cycles) ultrasound pulses is evaluated. Through ultra-high-speed microscopy it is shown that the bubbles produced early in the pulse from vaporized droplets are strongly affected by subsequent cycles of the vaporization pulse, and these effects increase with pulse length. Results show that decafluorobutane nanoemulsions with peak diameters on the order of 200 nm can be optimally vaporized with short pulses using pressures amenable to clinical diagnostic ultrasound machines.