IEEE Trans Ultrason Ferroelectr Freq Control. 2022 Dec;69(12):3255-3269. doi: 10.1109/TUFFC.2022.3212266. Epub 2022 Nov 24.
Boiling histotripsy (BH) is a mechanical tissue liquefaction method that uses sequences of millisecond-long high intensity focused ultrasound (HIFU) pulses with shock fronts. The BH treatment generates bubbles that move within the sonicated volume due to acoustic radiation force. Since the velocity of the bubbles and tissue debris is expected to depend on the lesion size and liquefaction completeness, it could provide a quantitative metric of the treatment progression. In this study, the motion of bubble remnants and tissue debris immediately following BH pulses was investigated using high-pulse repetition frequency (PRF) plane-wave color Doppler ultrasound in ex vivo myocardium tissue. A 256-element 1.5 MHz spiral HIFU array with a coaxially integrated ultrasound imaging probe (ATL P4-2) produced 10 ms BH pulses to form volumetric lesions with electronic beam steering. Prior to performing volumetric BH treatments, the motion of intact myocardium tissue and anticoagulated bovine blood following isolated BH pulses was assessed as two limiting cases. In the liquid blood the velocity of BH-induced streaming at the focus reached over 200 cm/s, whereas the intact tissue was observed to move toward the HIFU array consistent with elastic rebound of tissue. Over the course of volumetric BH treatments tissue motion at the focus locations was dependent on the axial size of the forming lesion relative to the corresponding size of the HIFU focal area. For axially small lesions, the maximum velocity after the BH pulse was directed toward the HIFU transducer and monotonically increased over time from about 20-100 cm/s as liquefaction progressed, then saturated when tissue was fully liquefied. For larger lesions obtained by merging multiple smaller lesions in the axial direction, the high-speed streaming away from the HIFU transducer was observed at the point of full liquefaction. Based on these observations, the maximum directional velocity and its location along the HIFU propagation axis were proposed and evaluated as candidate metrics of BH treatment completeness.
沸腾空化（BH）是一种机械组织液化方法，它使用具有激波前缘的毫秒级长高强度聚焦超声（HIFU）脉冲序列。BH 处理会产生气泡，由于声辐射力，这些气泡会在被超声处理的体积内移动。由于气泡和组织碎片的速度预计取决于病变大小和液化的完整性，因此它可以提供治疗进展的定量指标。在这项研究中，使用高脉冲重复频率（PRF）平面波彩色多普勒超声在离体心肌组织中研究了 BH 脉冲后立即的气泡残余物和组织碎片的运动。一个 256 元素的 1.5MHz 螺旋 HIFU 阵列与同轴集成的超声成像探头（ATL P4-2）产生了 10ms 的 BH 脉冲，以形成电子束转向的容积病变。在进行容积 BH 治疗之前，评估了在孤立 BH 脉冲后完整心肌组织和抗凝牛血的运动，这是两种极限情况。在液体血液中，在焦点处 BH 诱导的流动速度达到 200cm/s 以上，而观察到完整组织向 HIFU 阵列移动，这与组织的弹性回弹一致。在容积 BH 治疗过程中，焦点位置的组织运动取决于形成病变的轴向尺寸与相应的 HIFU 焦点区域尺寸的关系。对于轴向较小的病变，BH 脉冲后的最大速度指向 HIFU 换能器，并随着液化过程的进行从约 20-100cm/s 单调增加，然后在组织完全液化时饱和。对于在轴向方向上合并多个较小病变获得的较大病变，在完全液化时观察到远离 HIFU 换能器的高速流动。基于这些观察，提出并评估了最大定向速度及其在 HIFU 传播轴上的位置作为 BH 治疗完成度的候选指标。
