Abstract
This work investigated and compared the dynamic cavitation characteristics between low and high boiling-point phase-shift nanodroplets (NDs) under physiologically relevant flow conditions during focused ultrasound (FUS) exposures at different peak rarefactional pressures. A passive cavitation detection (PCD) system was used to monitor cavitation activity during FUS exposure at various acoustic pressure levels. Root mean square (RMS) amplitudes of broadband noise, spectrograms of the passive cavitation detection signals, and normalized inertial cavitation dose (ICD) values were calculated. Cavitation activity of low-boiling-point perfluoropentane (PFP) NDs and high boiling-point perfluorohexane (PFH) NDs flowing at in vitro mean velocities of 0-15cm/s were compared in a 4-mm diameter wall-less vessel in a transparent tissue-mimicking phantom. In the static state, both types of phase-shift NDs exhibit a sharp rise in cavitation intensity during initial FUS exposure. Under flow conditions, cavitation activity of the PFH NDs reached the steady state less rapidly compared to PFP NDs under the lower acoustic pressure (1.35MPa); at the higher acoustic pressure (1.65MPa), the RMS amplitude increased more sharply during the initial FUS exposure period. In particular, the RMS-time curves of the PFP NDs shifted upward as the mean flow velocity increased from 0 to 15cm/s; the RMS amplitude of the PFH ND solution increased from 0 to 10cm/s and decreased at 15cm/s. Moreover, amplitudes of the echo signal for the low boiling-point PFP NDs were higher compared to the high boiling-point PFH NDs in the lower frequency range, whereas the inverse occurred in the higher frequency range. Both PFP and PFH NDs showed increased cavitation activity in the higher frequency under the flow condition compared to the static state, especially PFH NDs. At 1.65MPa, normalized ICD values for PFH increased from 0.93±0.03 to 0.96±0.04 and from 0 to 10cm/s, then decreased to 0.86±0.05 at 15cm/s. This work contributes to our further understanding of cavitation characteristics of phase-shift NDs under physiologically relevant flow conditions during FUS exposure. In addition, the results provide a reference for selecting suitable phase-shift NDs to enhance the efficiency of cavitation-mediated ultrasonic applications.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.