The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Department of Biomedical Engineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, People's Republic of China.
Department of Radiology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, People's Republic of China.
Ultrasound Med Biol. 2019 Aug;45(8):2118-2132. doi: 10.1016/j.ultrasmedbio.2019.04.024. Epub 2019 May 29.
This study investigated and compared the time and frequency characteristics of cavitation activity between phase-shift nanodroplets (NDs) and lipid-shelled microbubbles (MBs) exposed to focused ultrasound (FUS) under physiologically relevant flow conditions. Root-mean-square (RMS) of broadband noise, spectrograms of the passive cavitation detection signals and inertial cavitation doses (ICDs) were calculated during FUS at varying mean flow velocities and two different peak-rarefactional pressures. At a lower pressure of 0.94 MPa, the mean values of the RMS amplitudes versus time for the NDs showed an upward trend but slowed down as the mean flow velocity increased. For flowing NDs, the rate of growth in RMS amplitudes within 2-5 MHz decreased more obviously than those within 5-8 MHz. At a higher pressure of 1.07 MPa, the increase in RMS amplitudes was accelerated as the mean flow velocity increased from 0 to 10 cm/s and slowed down as the mean flow velocity reached 15 cm/s. The general downward trends of RMS amplitudes for the MBs were retarded as the mean flow velocity increased at both acoustic pressures of 0.94 MPa and 1.07 MPa. At 0.94 MPa, the mean ICD value for the NDs decreased from 57 to 36 as the mean flow velocity increased from 0 to 20 cm/s. At 1.07 MPa, the mean ICD value initially increased from 45 to 57 as the mean flow velocity increased from 0 to 10 cm/s and subsequently decreased to 43 as the mean flow velocity reached 20 cm/s. For the MBs, the mean ICD value increased with increasing mean flow velocity at both acoustic pressures. These results could aid in future investigations of cavitation-enhanced FUS with the flowing phase-shift NDs and encapsulated, gas-filled MBs for various applications.
本研究在生理相关流动条件下，调查并比较了相移纳米液滴（NDs）和脂质壳微泡（MBs）在聚焦超声（FUS）下的空化活动的时间和频率特征。在不同平均流速和两种不同的峰值稀疏压力下，计算了 FUS 期间宽带噪声的均方根（RMS）、被动空化检测信号的声谱图和惯性空化剂量（ICD）。在较低的压力 0.94 MPa 下，NDs 的 RMS 振幅随时间的平均值呈上升趋势，但随着平均流速的增加而减慢。对于流动的 NDs，2-5 MHz 范围内 RMS 振幅的增长率比 5-8 MHz 范围内的增长率下降更为明显。在较高的压力 1.07 MPa 下，随着平均流速从 0 增加到 10 cm/s，RMS 振幅的增加速度加快，当平均流速达到 15 cm/s 时，增加速度减慢。在两种声压（0.94 MPa 和 1.07 MPa）下，随着平均流速的增加，MBs 的 RMS 振幅总体呈下降趋势，但速度较慢。在 0.94 MPa 下，随着平均流速从 0 增加到 20 cm/s，NDs 的平均 ICD 值从 57 降低到 36。在 1.07 MPa 下，随着平均流速从 0 增加到 10 cm/s，平均 ICD 值最初从 45 增加到 57，随后当平均流速达到 20 cm/s 时降低到 43。对于 MBs，在两种声压下，平均 ICD 值随着平均流速的增加而增加。这些结果可能有助于未来研究流动相移 NDs 和封装的充气 MBs 增强 FUS 的空化作用，用于各种应用。
