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BioMed Research International
Volume 2014, Article ID 518787, 10 pages
Research Article

In Vitro Demonstration of Focused Ultrasound Thrombolysis Using Bifrequency Excitation

1Inserm, U1032, LabTau and Université de Lyon, 69003 Lyon, France
2Université Lyon 1, 69003 Lyon, France
3Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
4Clinatec/LETI/CEA, 38054 Grenoble, France
5Radiology Department, University Hospitals of Geneva, 1211 Geneva, Switzerland
6Inserm, ADR 05 Rhône-Alpes, Auvergne, 69500 Bron, France

Received 17 March 2014; Revised 5 June 2014; Accepted 25 June 2014; Published 27 August 2014

Academic Editor: Rajiv Chopra

Copyright © 2014 Izella Saletes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Focused ultrasound involving inertial cavitation has been shown to be an efficient method to induce thrombolysis without any pharmacological agent. However, further investigation of the mechanisms involved and further optimization of the process are still required. The present work aims at studying the relevance of a bifrequency excitation compared to a classical monofrequency excitation to achieve thrombolysis without any pharmacological agent. In vitro human blood clots were placed at the focus of a piezoelectric transducer. Efficiency of the thrombolysis was assessed by weighing each clot before and after sonication. The efficiencies of mono- (550 kHz) and bifrequency (535 and 565 kHz) excitations were compared for peak power ranging from 70 W to 220 W. The thrombolysis efficiency appears to be correlated to the inertial cavitation activity quantified by passive acoustic listening. In the conditions of the experiment, the power needed to achieve 80% of thrombolysis with a monofrequency excitation is reduced by the half with a bifrequency excitation. The thermal effects of bifrequency and monofrequency excitations, studied using MR thermometry measurements in turkey muscle samples where no cavitation occurred, did not show any difference between both types of excitations when using the same power level.