Volume 2 Supplement 1

Abstracts of the 2nd European Symposium on Focused Ultrasound Therapy

Open Access

Inertial cavitation detection during in-vitro sonothrombolysis

  • Antonella Verbeni1Email author,
  • Andrea Cafarelli1,
  • Piero Miloro1 and
  • Arianna Menciassi1
Journal of Therapeutic Ultrasound20142(Suppl 1):A12

DOI: 10.1186/2050-5736-2-S1-A12

Published: 10 December 2014

Background

Being cardiovascular diseases the leading cause of death worldwide, a prompt intervention is needed to restore blood flow. Sonothrombolysis with/without addiction of thrombolytic drugs is explored as a promising solution, thanks to its non-invasiveness, precision and action quickness. Even if the involved mechanisms are not completely understood, acoustic cavitation seems to play a significant role [1]. Several efforts are currently devoted to optimizing sonication parameters [2]. A thorough investigation on the involved physical phenomena is expected to further speed-up the process.

Materials and methods

The experimental setup is composed of a Passive Cavitation Detector (PCD) recording pressure fluctuations of oscillating bubbles and mounted confocally to a 1MHz High Intensity Focused Ultrasound (HIFU) transducer. Confocality has been verified by mapping the pressure fields of both devices with a 0.2mm needle hydrophone.

An LDPE holder containing the thrombus is placed at the foci (Figure 1) through a 3 axis positioning frame. A constant flow of tap water (2ml/min) is established.
https://static-content.springer.com/image/art%3A10.1186%2F2050-5736-2-S1-A12/MediaObjects/40349_2014_Article_50_Fig1_HTML.jpg
Figure 1

CAD and picture of the experimental setup.

To detect inertial cavitation (broadband emission and increase in white noise), the PCD signal has been filtered analogically at 5MHz to remove harmonic frequencies which could saturate the acquisition system.

Results

In-vitro sonothrombolysis tests have been performed on human blood clots exposed for two minutes to an acoustic field acoustic field (65W power, 25mm focal length, 3mm focal diameter, 450μs pulse length, 1:10 duty cycle). The same parameters were previously credited to avoid thermal damage [3].

During the test, PCD signal was digitalized twice per second, at a sample frequency of 40MHz, synchronized with the HIFU burst. Power spectral density was calculated in the 5-12MHz band, with digital notch filters at the super-harmonic frequencies, in order to quantify the cavitation dose. Figure 2 shows the results of a sonothrombolysis test. A temporal correlation between thrombolysis inception and white noise increase can be observed.
https://static-content.springer.com/image/art%3A10.1186%2F2050-5736-2-S1-A12/MediaObjects/40349_2014_Article_50_Fig2_HTML.jpg
Figure 2

Power spectral density of the signal acquired by the PCD (left) and screenshots from a synchronized video during the thrombolysis test (right).

Conclusion

The proposed setup demonstrated the ability to detect inertial cavitation during in-vitro sonothrombolysis tests; a correlation between thrombolysis inception and white noise increase was found. Statistically significant analysis will be performed to verify this correlation, thus allowing the optimization of sonothrombolysis parameters and protocols to enhance cavitational effects.

Declarations

Acknowledgement

This work was partially supported by Fondazione Pisa in the framework of the MicroVAST project.

Authors’ Affiliations

(1)
The BioRobotics Institute, Scuola Superiore Sant’Anna

References

  1. Medel R, Crowley W, McKisic MS, Dumont AS, Kassell NF: Sonothrombolysis: an emerging modality for the management of stroke. Neurosurgery. 2009, 65: 979-993. 10.1227/01.NEU.0000350226.30382.98.View ArticlePubMedGoogle Scholar
  2. Hölscher T, Raman R, Fisher DJ, Ahadi G, Zadicario E, Voie A: Effects of varying duty cycle and pulse width on high-intensity focused ultrasound (HIFU) induced transcranial thrombolysis. J Ther Ultrasound. 2013, 1: 18-10.1186/2050-5736-1-18.PubMed CentralView ArticlePubMedGoogle Scholar
  3. Cafarelli A, Verbeni A, Miloro P, Menciassi A: Qualitative Assessment of Thermal Effects in High Intensity Ultrasound Thrombolysis Experiments. Presented at the 25th International Conference of the Society for Medical Innovation and Technology (iSMIT). 2013, Baden-Baden, GermanyGoogle Scholar

Copyright

© Verbeni et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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