State Key Laboratory of Ultrasound Engineering in Medicine Co-founded by Chongqing and the Ministry of Science and Technology, Chongqing Collaborative Innovation Center for Minimally Invasive and Noninvasive Medicine, College of Biomedical Engineering, Chongqing Medical University, Chongqing, 400016, China.
College of Stomatology, Chongqing Medical University, Chongqing, 401147, China.
J Ultrasound Med. 2020 Feb;39(2):259-271. doi: 10.1002/jum.15098. Epub 2019 Jul 24.
To compare the efficacy of pulsed high-intensity focused ultrasound (PHIFU) versus continuous high-intensity focused ultrasound (CHIFU) ablation at identical doses.
Continuous and pulsed HIFU (1200 J) at duty cycles (DCs) of 60% and 20% were examined for their capacity to ablate bovine liver tissue in vitro and rabbit liver tissue in vivo. After ablation, grayscale changes and pathologic characteristics were observed or measured, and the tissue necrosis volume, energy efficiency factor, and average grayscale density were calculated.
The pulsed mode generated greater liquefaction necrosis. An inconspicuous grayscale change was observed for PHIFU at a DC of 20% in some samples, which appeared as an elliptical cavity. The energy efficiency factor of PHIFU at a DC of 60% was significantly lower than that of CHIFU, as observed both in vitro and in vivo (P < .05). The grayscale value and average grayscale density in response to CHIFU were significantly greater than those in response to PHIFU (60% or 20%; P < .05). Histopathologic analysis revealed liquefaction necrosis in all PHIFU groups.
At identical doses, compared with CHIFU, a single session of PHIFU can generate liquefaction necrosis and at a higher DC can improve ablation efficiency. This increased efficacy of PHIFU may involve enhancement of tissue destruction by cavitation effects and a reduction in the obstruction effect of endogenous microbubbles through cavitation effects or a more effective diffusion of heat.
比较在相同剂量下脉冲高强度聚焦超声（PHIFU）与连续高强度聚焦超声（CHIFU）消融的疗效。
在体外牛肝组织和体内兔肝组织中，分别检查 60%和 20%占空比的连续和脉冲 HIFU（1200 J）消融能力。消融后，观察或测量灰度变化和病理特征，并计算组织坏死体积、能量效率因子和平均灰度密度。
脉冲模式产生更大的液化性坏死。在一些样本中，观察到 PHIFU 的 20%占空比时灰度变化不明显，呈椭圆形腔。在体外和体内，PHIFU 的 60%占空比的能量效率因子均明显低于 CHIFU（P < .05）。CHIFU 引起的灰度值和平均灰度密度明显大于 PHIFU（60%或 20%；P < .05）。组织病理学分析显示所有 PHIFU 组均发生液化性坏死。
在相同剂量下，与 CHIFU 相比，单次 PHIFU 可产生液化性坏死，较高的占空比可提高消融效率。PHIFU 这种增效作用可能涉及空化效应增强组织破坏，以及通过空化效应减少内源性微泡的阻塞效应或更有效的热扩散。
