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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Histotripsy-induced cavitation cloud initiation thresholds in tissues of different mechanical properties
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Histotripsy-induced cavitation cloud initiation thresholds in tissues of different mechanical properties

机译：具有不同机械特性的组织中的组织变性诱导的空化云起始阈值

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Histotripsy is an ultrasound ablation method that depends on the initiation and maintenance of a cavitation bubble cloud to fractionate soft tissue. This paper studies how tissue properties impact the pressure threshold to initiate the cavitation bubble cloud. Our previous study showed that shock scattering off one or more initial bubbles, expanded to sufficient size in the focus, plays an important role in initiating a dense cavitation cloud. In this process, the shock scattering causes the positive pressure phase to be inverted, resulting in a scattered wave that has the opposite polarity of the incident shock. The inverted shock is superimposed on the incident negative pressure phase to form extremely high negative pressures, resulting in a dense cavitation cloud growing toward the transducer. We hypothesize that increased tissue stiffness impedes the expansion of initial bubbles, reducing the scattered tensile pressure, and thus requiring higher initial intensities for cloud initiation. To test this hypothesis, 5-cycle histotripsy pulses at pulse repetition frequencies (PRFs) of 10, 100, or 1000 Hz were applied by a 1-MHz transducer focused inside mechanically tunable tissue-mimicking agarose phantoms and various ex vivo porcine tissues covering a range of Young?????????s moduli. The threshold to initiate a cavitation cloud and resulting bubble expansion were recorded using acoustic backscatter detection and optical imaging. In both phantoms and ex vivo tissue, results demonstrated a higher cavitation cloud initiation threshold for tissues of higher Young?????????s modulus. Results also demonstrated a decrease in bubble expansion in phantoms of higher Young?????????s modulus. These results support our hypothesis, improve our understanding of the effect of histotripsy in tissues with different mechanical properties, and provide a rational basis to tailor acoustic parameters for fractionation of specific tissues.
机译：组织碎裂术是一种超声消融方法，它依赖于空化气泡云的启动和维持来分离软组织。本文研究了组织特性如何影响压力阈值以引发空化气泡云。我们以前的研究表明，震荡从一个或多个初始气泡中散发出来，在焦点处扩展到足够大的尺寸，在引发致密的空化云中起着重要作用。在此过程中，冲击波的散射会导致正压相位反转，从而导致散射波具有与入射冲击相反的极性。倒转的冲击叠加在入射的负压相上以形成极高的负压，导致致密的空化云向换能器生长。我们假设增加的组织刚度会阻止初始气泡的膨胀，从而降低分散的拉伸压力，因此需要更高的初始强度才能开始云雾。为了验证这一假设，通过将1 MHz传感器聚焦在机械可调谐的组织模拟琼脂糖体模和覆盖了动物体内的各种离体猪组织中，以10、100或1000 Hz的脉冲重复频率（PRF）施加5个周期的组织周期脉冲。杨氏模量的范围。使用声反向散射检测和光学成像记录了引发空化云并导致气泡膨胀的阈值。在体模和离体组织中，结果均表明，较高杨氏模量组织的空化云起始阈值较高。结果还表明，较高杨氏模量的体模中的气泡膨胀减少。这些结果支持了我们的假设，增进了我们对具有不同机械特性的组织中组织曲霉病作用的理解，并为调整用于特定组织分级的声学参数提供了合理的基础。

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