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首页> 外文期刊>Physics in medicine and biology. >In vivo bubble nucleation probability in sheep brain tissue.
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In vivo bubble nucleation probability in sheep brain tissue.

机译：绵羊脑组织中体内气泡成核的可能性。

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摘要

Gas nuclei exist naturally in living bodies. Their activation initiates cavitation activity, and is possible using short ultrasonic excitations of high amplitude. However, little is known about the nuclei population in vivo, and therefore about the rarefaction pressure required to form bubbles in tissue. A novel method dedicated to in vivo investigations was used here that combines passive and active cavitation detection with a multi-element linear ultrasound probe (4-7 MHz). Experiments were performed in vivo on the brain of trepanated sheep. Bubble nucleation was induced using a focused single-element transducer (central frequency 660 kHz, f-number = 1) driven by a high power (up to 5 kW) electric burst of two cycles. Successive passive recording and ultrafast active imaging were shown to allow detection of a single nucleation event in brain tissue in vivo. Experiments carried out on eight sheep allowed statistical studies of the bubble nucleation process. The nucleation probability was evaluated as a function of the peak negative pressure. No nucleation event could be detected with a peak negative pressure weaker than -12.7 MPa, i.e. one order of magnitude higher than the recommendations based on the mechanical index. Below this threshold, bubble nucleation in vivo in brain tissues is a random phenomenon.
机译：气核自然存在于生物体内。它们的激活会引发空化活动，并且可以通过短时高振幅的超声激发来实现。然而，对于体内的核种群，以及因此在组织中形成气泡所需的稀疏压力，人们所知甚少。这里使用了一种专门用于体内研究的新方法，该方法将被动和主动空化检测与多元素线性超声探头（4-7 MHz）相结合。在被羊的大脑中进行了体内实验。使用聚焦的单元素换能器（中心频率660 kHz，f值= 1），由两个周期的高功率（高达5 kW）电脉冲驱动，诱导气泡成核。连续的被动记录和超快的主动成像显示可以检测体内脑组织中的单个成核事件。在八只绵羊上进行的实验允许对气泡成核过程进行统计研究。评估成核概率与峰值负压的关系。如果峰值负压小于-12.7 MPa，即比基于机械指标的建议值高一个数量级，则无法检测到任何成核事件。低于该阈值，脑组织中的体内气泡成核是随机现象。

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