Song Minho, Thomas Gilles P L, Khokhlova Vera A, Wang Yak-Nam, Totten Stephanie I, Sapozhnikov Oleg A, Schade George R, Khokhlova Tatiana
Division of Gastroenterology, University of Washington School of Medicine, Seattle, WA, United States of America.
Center for Industrial and Medical Ultrasound, University of Washington, Seattle, WA, United States of America.
Ultrasonics. 2025 Jul 29;156:107775. doi: 10.1016/j.ultras.2025.107775.
Boiling histotripsy (BH) is a promising method for mechanical tissue fractionation and liquefaction, utilizing millisecond-long high-intensity focused ultrasound (HIFU) pulses with shock fronts. Recent study has reported that cavitation bubbles induced during the BH pulse can move within the liquefied treated volume for a few milliseconds to seconds after each BH pulse ends. These bubble motions can be observed by ultrasound Doppler measurements, with maximum Doppler velocity showing significant potential as a metric to determine the treatment completion, as previously demonstrated in ex vivo setting. Here, this velocity metric was tested based on the results of in vivo pig experiments, along with tissue liquefaction levels evaluated from histology. A 256-element 1.5 MHz spiral HIFU array with a center opening for the imaging probe installation was used for BH pulse control. A sequence of 10 ms BH pulses with a 1 Hz pulse repetition frequency (PRF) was delivered to the predesigned two-dimensional target grid to generate large liquefied volumes. A small aperture (around 2 cm) imaging probe was mounted at the center opening of HIFU transducer and used for planewave Doppler and B-mode imaging. To increase the maximum measurable Doppler velocity, a high PRF regime was applied instead of the conventional pulse-echo regime. The results showed that the maximum velocity increased over the treatment from 40 to 100 cm/s as the tissue progressively changed from intact to completely liquefied. The distribution of elevational averaged maximum velocity along the lateral target volumes aligned well with the lesion shown in the corresponding histological image and statistically significantly correlated with the liquefaction grade. A maximum velocity above 84 cm/s ensured the complete liquefaction level, reinforcing its potential as a metric to determine successful treatment.
沸腾组织粉碎术（BH）是一种用于机械性组织破碎和液化的很有前景的方法，它利用带有冲击波前沿的毫秒级高强度聚焦超声（HIFU）脉冲。最近的研究报告称，在BH脉冲期间诱导产生的空化气泡在每个BH脉冲结束后的几毫秒到几秒内可在液化的治疗区域内移动。这些气泡运动可通过超声多普勒测量来观察，如之前在体外实验中所证明的，最大多普勒速度显示出作为确定治疗完成情况的指标具有显著潜力。在此，基于体内猪实验的结果对该速度指标进行了测试，并结合从组织学评估的组织液化水平进行分析。使用了一个带有用于安装成像探头的中心开口的256阵元1.5MHz螺旋HIFU阵列来控制BH脉冲。以1Hz的脉冲重复频率（PRF）发送一系列10ms的BH脉冲到预先设计的二维目标网格，以产生大的液化区域。一个小孔径（约2cm）的成像探头安装在HIFU换能器的中心开口处，用于平面波多普勒和B模式成像。为了提高最大可测多普勒速度，采用了高PRF模式而非传统的脉冲回波模式。结果表明，随着组织从完整逐渐变为完全液化，治疗过程中最大速度从40cm/s增加到100cm/s。沿横向目标区域的仰角平均最大速度分布与相应组织学图像中显示的损伤区域吻合良好，并且与液化等级在统计学上显著相关。最大速度高于84cm/s确保了完全液化水平，增强了其作为确定治疗成功的指标的潜力。
