Removal of Residual Cavitation Nuclei to Enhance Histotripsy Fractionation of Soft Tissue
Removal of Residual Cavitation Nuclei to Enhance Histotripsy Fractionation of Soft Tissue
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DOI：
10.1109/tuffc.2015.007202
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发表时间：
2015-12-01
影响因子：
3.6
通讯作者：
Hall, Timothy L.
中科院分区：
文献类型：
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作者：
Duryea, Alexander P.;Cain, Charles A.;Hall, Timothy L.
由初级空化崩溃产生的残余气泡核可以限制组织破碎软组织分离的效率。当这些残留气泡从一个组织摧毁脉冲持续到下一个时，它们可以在焦点体积内的一组离散位点处引发空化气泡的重复成核。这种效应-称为空化记忆-表现为损伤形成效率低下，因为病灶体积内的某些部位治疗过度，而其他部位治疗不足。虽然空化记忆效应可以通过使用低脉冲重复频率（PRF）来被动地减轻，该低脉冲重复频率（PRF）在连续的脉冲之间为修复核提供足够的溶解时间，但是这种低PRF也导致缓慢的损伤产生。因此，当使用高得多的PRF时，将非常期望保持与低脉冲速率相关联的高的每脉冲效率。在这条静脉中，我们已经开发出一种策略，用于主动去除的气泡核后，初级空化崩溃，使用低振幅的超声序列（称为气泡去除序列），以刺激这些气泡的聚集和随后的合并。在这项研究中，气泡去除序列被纳入红细胞组织模拟体模的高PRF组织破坏治疗（100 Hz）中，该体模允许真实的时间内病变发展的可视化。还在1 Hz的低PRF下进行了一系列参考处理，以提供空化记忆效应最小的比较点。发现当使用100 Hz的高得多的脉冲速率时，短至1 ms的气泡去除序列能够保持与1 Hz的低PRF相关的有效损伤发展特征。然后将这些结果扩展到组织体模内大体积的治疗，并利用针对单焦点情况确定的最佳气泡去除序列以高速均质化10 x 10 mm区域。
Remanent bubble nuclei generated by primary cavitation collapse can limit the efficiency of histotripsy soft-tissue fractionation. When these residual bubbles persist from one histotripsy pulse to the next, they can seed the repetitive nucleation of cavitation bubbles at a discrete set of sites within the focal volume. This effect-referred to as cavitation memory-manifests in inefficient lesion formation, because certain sites within the focal volume are overtreated whereas others remain undertreated. Although the cavitation memory effect can be passively mitigated by using a low pulse repetition frequency (PRF) that affords remanent nuclei sufficient time for dissolution between successive pulses, this low PRF also results in slow lesion production. As such, it would be highly desirable to maintain the high per-pulse efficiency associated with low pulse rates when much higher PRFs are utilized. In this vein, we have developed a strategy for the active removal of the remanent bubble nuclei following primary cavitation collapse, using low-amplitude ultrasound sequences (termed bubble-removal sequences) to stimulate the aggregation and subsequent coalescence of these bubbles. In this study, bubble-removal sequences were incorporated in high-PRF histotripsy treatment (100 Hz) of a red blood cell tissue-mimicking phantom that allows for the visualization of lesion development in real time. A series of reference treatments were also conducted at the low PRF of 1 Hz to provide a point of comparison for which cavitation memory effects are minimal. It was found that bubble-removal sequences as short as 1 ms are capable of maintaining the efficacious lesion development characteristics associated with the low PRF of 1 Hz when the much higher pulse rate of 100 Hz is used. These results were then extended to the treatment of a large volume within the tissue phantom, and optimal bubble-removal sequences identified for the single-focal-spot case were utilized to homogenize a 10 x 10 mm region at high rate.