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Accueil du site > Productions scientifiques > Thèses > Thèses soutenues > Détection et caractérisation de la destruction des microbulles de produit de contraste ultrasonore.

Détection et caractérisation de la destruction des microbulles de produit de contraste ultrasonore.

Doctoral Research Scientist : Azzdine AMMI

Thesis Director : S. Lori BRIDAL

Research topic : Detection and characterization of ultrasound contrast agent microbubble destruction.

Etablissement : Université Pierre et Marie Curie Paris VI

Date of defense :

Summary :

Ultrasound contrast agents present a significant potential for imaging and therapy. This potential is linked to a better understanding of the destruction phenomena of the microbubbles present in these agents. The aim of this work was to detect, characterize and quantify destruction of isolated ultrasound contrast agent microbubbles. The tools applied toward this objective were a model for nonlinear shelled-bubble-wall dynamics (modified Herring equation) and three in vitro experimental systems. Post-excitation acoustic emissions were detected using the first experimental system (passive cavitation detector). These emissions are shown to be linked to inertial cavitation events following microbubble shell rupture. This link is illustrated with the microbubble dynamics model. Thereupon, an automatic algorithm is developed to detect the post-excitation signals. Destruction thresholds and percent occurrence of destruction for OptisonTM microbubbles are estimated using these post-excitation signals for three frequencies (0.9, 2.8 and4.6 MHz) and three durations (3, 5 and7) of the incident acoustic pulse across a range of incident peak rarefactional pressures from 0.07 to 5.39 MPa. The second system consisting of a double passive cavitation detector was used to compare the temporal and spectral response of oscillating and ruptured microbubbles across a large bandwidth, including the transmit bandwidth. The third system permitted verification by optical microscopy that post-excitation signals were present only when the microbubble was destroyed. The post-excitation signals provide an acoustic signature of the microbubble destruction and enable the characterization and the quantification of destruction.

Key words : Ultrasound contrast agent, threshold, OptisonTM, post-excitation, inertial cavitation, shell rupture, microbubble.

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