Rapid short-pulse sequences enhance the spatiotemporal uniformity of acoustically driven microbubble activity during flow conditions
File(s)JASA accepted manuscript.pdf (615.01 KB)
Accepted version
Author(s)
Type
Journal Article
Abstract
Despite the promise of microbubble-mediated focused ultrasound therapies, in vivo findings have revealed over-treated and under-treated regions distributed throughout the focal volume. This poor distribution cannot be improved by conventional pulse shapes and sequences, due to their limited ability to control acoustic cavitation dynamics within the ultrasonic focus. This paper describes the design of a rapid short-pulse (RaSP) sequence which is comprised of short pulses separated by μs off-time intervals. Improved acoustic cavitation distribution was based on the hypothesis that microbubbles can freely move during the pulse off-times. Flowing SonoVue® microbubbles (flow velocity: 10 mm/s) were sonicated with a 0.5 MHz focused ultrasound transducer using RaSP sequences (peak-rarefactional pressures: 146–900 kPa, pulse repetition frequency: 1.25 kHz, and pulse lengths: 5–50 cycles). The distribution of cavitation activity was evaluated using passive acoustic mapping. RaSP sequences generated uniform distributions within the focus in contrast to long pulses (50 000 cycles) that produced non-uniform distributions. Fast microbubble destruction occurred for long pulses, whereas microbubble activity was sustained for longer durations for shorter pulses. High-speed microscopy revealed increased mobility in the direction of flow during RaSP sonication. In conclusion, RaSP sequences produced spatiotemporally uniform cavitation distributions and could result in efficient therapies by spreading cavitation throughout the treatment area.
Date Issued
2016-10-11
Date Acceptance
2016-09-13
Citation
Journal of the Acoustical Society of America, 2016, 140 (4)
ISSN
0001-4966
Publisher
Acoustical Society of America
Journal / Book Title
Journal of the Acoustical Society of America
Volume
140
Issue
4
Copyright Statement
© 2016 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in The Journal of the Acoustical Society of America and may be found at http://dx.doi.org/10.1121/1.4964271.
Sponsor
Wellcome Trust
Grant Number
097816/Z/11/B
Subjects
Acoustics
MD Multidisciplinary
Publication Status
Published
Article Number
2469