Ayache Bouakaz - Academia.edu (original) (raw)

Papers by Ayache Bouakaz

Ultrasound in Medicine & Biology, 1997

The intravascular ultrasound image of the intrahnninal contour depends on the difference between ... more The intravascular ultrasound image of the intrahnninal contour depends on the difference between acoustic impedances of the medii which create the endoluminal interface. There are several limitations to the visualization and detection of this interface. These limitations are due to artifacts encountered during image formation and to anatomical complexity. The purpose of this study is to obtain intrakmhnd contour enhancement using ultrasound contrast agent (UCA). Therefore, our objective was to address the feasibility of this technique by documenting the following: (i) the acoustic properties of UCA at 30 MI&; (ii) in vitro experimentation with tube or postnecrotic artery; and (iii) suitable digital processing. The images obtah& with UCA (enhanced image quality) and subtracted from those without UCA provided, after simple dfgital processing, accurate visualization of the arterial lumen. The image obtained exhibits an even, high-contrast intraluminal edge. Such characteristics facilitate contour extraction by the automated contour detection procedures. 0 1997 World Federation for Ultrasound in Medicine and Biology.

Physics in Medicine and Biology, 2015

Both in vitro and in vivo, contrast agent microbubbles move near bounding surfaces, such as the w... more Both in vitro and in vivo, contrast agent microbubbles move near bounding surfaces, such as the wall of an experimental container or the wall of a blood vessel. This problem inspires interest in theoretical models that predict the effect of a wall on the dynamics of a contrast microbubble. There are models for a bubble at a large distance from a wall and for a bubble adherent to a wall. The aim of the present study is to develop a generalized model that describes the dynamics of a contrast microbubble at arbitrary distances from a wall and thereby make it possible to simulate the acoustic response of the bubble starting from large separation distances up to contact between the bubble and the wall. The wall is assumed to be a plane. Therefore, the developed model applies for in vitro investigations of contrast agents in experimental containers. It can also be used as a first approximation to the case of a contrast microbubble within a large blood vessel. The derivation of the model is based on the multipole expansion of the bubble velocity potential, the image source method, and the Lagrangian formalism. The model consists of two coupled equations, one of which describes the bubble radial oscillation and the second describes the translation of the bubble center. Numerical simulations are performed to determine how the acoustic response of a contrast microbubble depends on the separation distance near walls of different types: rigid, plastic, arterial, etc. The dynamics of the bubble encapsulation is described by the Marmottant shell model. The properties of the plastic wall correspond to OptiCell chambers commonly used in experiments. The results of the simulations show that the bubble resonance frequency near a wall depends on both the separation distance and the wall material properties. In particular, the rigid wall makes the resonance frequency decrease with decreasing separation distance, whereas in the vicinity of the OptiCell wall and the arterial wall, the resonance frequency increases. The theoretical model is validated by comparing with experimental Institute of Physics and Engineering in Medicine . 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909

Targeted drug delivery under image guidance is gaining more interest in the drug-delivery field. ... more Targeted drug delivery under image guidance is gaining more interest in the drug-delivery field. The use of microbubbles as contrast agents in diagnostic ultrasound provides new opportunities in noninvasive image-guided drug delivery. In the present study, the imaging and therapeutic properties of novel doxorubicin liposome-loaded microbubbles are evaluated. The results showed that at scanning settings (1.7 MHz and mechanical index 0.2), these microbubbles scatter sufficient signal for nonlinear ultrasound imaging and can thus be imaged in real time and be tracked in vivo. In vitro therapeutic evaluation showed that ultrasound at 1 MHz and pressures up to 600 kPa in combination with the doxorubicin liposomeloaded microbubbles induced 4-fold decrease of cell viability compared with treatment with free doxorubicin or doxorubicin liposome-loaded microbubbles alone. The therapeutic effectiveness is correlated to an ultrasound-triggered release of doxorubicin from the liposomes and an enhanced uptake of the free doxorubicin by glioblastoma cells. The results obtained demonstrate that the combination of ultrasound and the doxorubicin liposome-loaded microbubbles can provide a new method of noninvasive image-guided drug delivery. ). c. Mannaris and M. averkiou are with the department of Mechanical and Manufacturing Engineering, University of cyprus, nicosia, cyprus. B. Geers and I. lentacker are with the laboratory

Thin solid shell contrast agents bubbles are expected to undergo different volume oscillating beh... more Thin solid shell contrast agents bubbles are expected to undergo different volume oscillating behaviors when the acoustic power is increased: small oscillations when the shell remains spherical, and large oscillations when the shell buckles. Contrary to bubbles covered with thin lipidic monolayers that buckle as soon as compressed, solid shell bubbles resist compression, making the buckling transition abrupt. Numerical simulations that explicitly incorporate a shell bending modulus give the critical buckling pressure and post-buckling shape, and show the appearance of a finite number of wrinkles. These findings are incorporated in a model based on the concept of effective surface tension. This model compares favorably to experiments when adjusting two main parameters: the buckling tension and the rupture shell tension. The buckling tension provides a direct estimation of the acoustic pressure threshold at which buckling occurs. PACS numbers: 43.25.Yw Nonlinear acoustics of bubbly liquids, 43.35.Ei Acoustic cavitation in liquids, 46.32.+x Static buckling and instability Buckling resistance of solid shell bubbles 1

The sequence proposed follows the same principle than BVM but with changes on the amplitude coeff... more The sequence proposed follows the same principle than BVM but with changes on the amplitude coefficient. Instead of sending acoustic waves with simple, double and triple bias voltage, the coefficient are equal to 1, (λ+1) and (2λ+1). Taking λ=1 gives the same coefficient than the classical BVM method.

Microbubbles, either in the form of free gas bubbles surrounded by a fluid or encapsulated bubble... more Microbubbles, either in the form of free gas bubbles surrounded by a fluid or encapsulated bubbles used currently as contrast agents for medical echography, exhibit complex dynamics under specific acoustic excitations. Nonetheless, considering their micron size and the complexity of their interaction phenomenon with ultrasound waves, expensive and complex experiments and/or simulations are required for their analysis. The behavior of a microbubble along its equator can be linked to a system of coupled oscillators. In this study, the oscillatory behavior of a microbubble has been investigated through an acousto-mechanical analogy based on a ring-shaped chain of coupled pendula. Observation of parametric vibration modes of the pendula ring excited at frequencies between 1 and 5 Hz is presented. Simulations have been carried out and show mode mixing phenomena. The relevance of the analogy between a microbubble and the macroscopic acousto-mechanical setup is discussed and suggested as an alternative way to investigate the complexity of microbubble dynamics.

Imagerie de contraste adaptative : optimisation de la fréquence d'émission. Colloque IMVIE 5 Imag... more Imagerie de contraste adaptative : optimisation de la fréquence d'émission. Colloque IMVIE 5 Imagerie pour les sciences du vivant et la médecine, Jul 2009, Mulhouse, France. HAL Id: hal-00607265 https://hal.archives-ouvertes.fr/hal-00607265

Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use... more Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles.

Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use... more Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles.

Physics Procedia, 2015

Rationale and aim: In the field of ultrasonic contrast agent imaging, Capacitive Micromachined Ul... more Rationale and aim: In the field of ultrasonic contrast agent imaging, Capacitive Micromachined Ultrasonic Transducer (cMUT) are of great interest because of their wide frequency bandwidth. However, due to their intrinsic nonlinear behaviour, their use with classical nonlinear imaging techniques (pulse inversion, amplitude modulation, harmonic imaging...) is still limited. Different approaches have been proposed to suppress the nonlinear part of the emitting signal from a cMUT. Recently, a new imaging sequence called Bias Voltage Modulation (BVM) has shown very good potential but is limited to the conventional regime of the probe (well below the collapse voltage). Thus the probe's sensitivity is not optimized. Materials and methods: An improved version of the BVM sequences is proposed to allow the use of bias voltages close to the collapse voltage. The principle is to change the coefficients associated with the successive pulses of the sequence. Experiments have been performed using a 128-element cMUT probe connected to an open scanner. For microbubbles measurements, Sonovue contrast agents have been imaged through a flow phantom. A contrast to tissue ratio (CTR) and a signal to noise ratio (SNR) were calculated to assess the efficacy of the new approach. Results: The application of BVM sequence with new coefficients show an increase of the CTR of 19 dB at high bias voltage (90% of the collapse) compared to the classical BVM sequence. Due to the high sensitivity of the probe in this regime, the SNR is also increased by 9 dB. These results reveal that the BVM sequence can be optimized further and applied at bias voltage close to the collapse and thus fully exploit the potential of the cMUT technology for contrast agent imaging.

Ultraschall in der Medizin - European Journal of Ultrasound, 2015

The subject of this study is shear stress exerted on the cell membrane by acoustic microstreaming... more The subject of this study is shear stress exerted on the cell membrane by acoustic microstreaming generated by a contrast microbubble pulsating nearby a cell. This effect is presumed to play a major role in the sonoporation process. Currently, the existing model of this effect is based on an equation that has been derived for a free hemispherical bubble resting on a rigid plane. Such a model is not adequate for an encapsulated bubble such as a contrast agent microbubble. In this study, an improved theory is suggested that assumes an encapsulated bubble to be detached from the cell membrane. The new model allows one to calculate the shear stress distribution on the cell membrane and to determine the position and the magnitude of the peak shear stress at different values of the acoustic parameters. The second problem under consideration is how to apply the model for pairwise bubble-cell interactions to bubble-cell solutions which one has to deal with in experiments. An approach is proposed to evaluate the number of cells undergoing sonoporation in a bubble-cell solution. It is shown that the reaction of a bubble-cell solution to the variation of the acoustic parameters can be different from what is expected from the analysis of pairwise interactions between single bubbles and cells. In particular, the attenuation of the driving acoustic wave caused by bubbles can considerably reduce the total efficiency of sonoporation in the solution at frequencies close to the resonance frequency of bubbles of dominant size. Numerical examples for a polydisperse bubble population are presented.

This chapter is devoted to the dynamics of encapsulated gas microbubbles which are used as contra... more This chapter is devoted to the dynamics of encapsulated gas microbubbles which are used as contrast agents and a vehicle for targeted drug delivery in medical ultrasonics. Topics covered include theoretical models describing the effect of encapsulation on the acoustic response of contrast microbubbles, models describing the interaction of contrast microbubbles with boundaries such as walls of experimental containers and blood vessels, ultrasound imaging techniques based on using microbubble contrast agents, and the phenomenon of sonoporation which is believed to open great possibilities for targeted drug delivery by means of contrast microbubbles. The chapter reviews recent results obtained in these areas.

Le développement de nouvelles technologies permettant un diagnostic précoce des cancers est essen... more Le développement de nouvelles technologies permettant un diagnostic précoce des cancers est essentiel. L'utilisation de microbulles spécifiques reconnaissant leurs cibles permet de détecter de façon sensible les sites pathologiques ciblés (e.g. tumeurs). Le but de cette analyse est de fournir une base pour des investigations de réponse acoustique des agents de contraste ciblés qui oscillent près d'une paroi imitant la paroi vasculaire. Nous proposons plus particulièrement d'utiliser un modèle de la dynamique de la bulle qui tient compte du phénomène acoustique « compression only » (Marmottant,2005). Nous allons exploiter ce phénomène pour la détection de microbulles ciblées. À cet effet, nous avons résolu l'équation d'oscillation radiale pour une bulle encapsulée à proximité d'une paroi rigide et calculer l'écho diffusé par la microbulle. En utilisant différentes conditions d'excitation et pour des microbulles de tailles différentes. L'écho en pro...

Ultrasound in Medicine & Biology, 1997

The intravascular ultrasound image of the intrahnninal contour depends on the difference between ... more The intravascular ultrasound image of the intrahnninal contour depends on the difference between acoustic impedances of the medii which create the endoluminal interface. There are several limitations to the visualization and detection of this interface. These limitations are due to artifacts encountered during image formation and to anatomical complexity. The purpose of this study is to obtain intrakmhnd contour enhancement using ultrasound contrast agent (UCA). Therefore, our objective was to address the feasibility of this technique by documenting the following: (i) the acoustic properties of UCA at 30 MI&; (ii) in vitro experimentation with tube or postnecrotic artery; and (iii) suitable digital processing. The images obtah& with UCA (enhanced image quality) and subtracted from those without UCA provided, after simple dfgital processing, accurate visualization of the arterial lumen. The image obtained exhibits an even, high-contrast intraluminal edge. Such characteristics facilitate contour extraction by the automated contour detection procedures. 0 1997 World Federation for Ultrasound in Medicine and Biology.

Physics in Medicine and Biology, 2015

Both in vitro and in vivo, contrast agent microbubbles move near bounding surfaces, such as the w... more Both in vitro and in vivo, contrast agent microbubbles move near bounding surfaces, such as the wall of an experimental container or the wall of a blood vessel. This problem inspires interest in theoretical models that predict the effect of a wall on the dynamics of a contrast microbubble. There are models for a bubble at a large distance from a wall and for a bubble adherent to a wall. The aim of the present study is to develop a generalized model that describes the dynamics of a contrast microbubble at arbitrary distances from a wall and thereby make it possible to simulate the acoustic response of the bubble starting from large separation distances up to contact between the bubble and the wall. The wall is assumed to be a plane. Therefore, the developed model applies for in vitro investigations of contrast agents in experimental containers. It can also be used as a first approximation to the case of a contrast microbubble within a large blood vessel. The derivation of the model is based on the multipole expansion of the bubble velocity potential, the image source method, and the Lagrangian formalism. The model consists of two coupled equations, one of which describes the bubble radial oscillation and the second describes the translation of the bubble center. Numerical simulations are performed to determine how the acoustic response of a contrast microbubble depends on the separation distance near walls of different types: rigid, plastic, arterial, etc. The dynamics of the bubble encapsulation is described by the Marmottant shell model. The properties of the plastic wall correspond to OptiCell chambers commonly used in experiments. The results of the simulations show that the bubble resonance frequency near a wall depends on both the separation distance and the wall material properties. In particular, the rigid wall makes the resonance frequency decrease with decreasing separation distance, whereas in the vicinity of the OptiCell wall and the arterial wall, the resonance frequency increases. The theoretical model is validated by comparing with experimental Institute of Physics and Engineering in Medicine . 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909 Al A Doinikov and A Bouakaz Phys. Med. Biol. 60 (2015) 7909

Targeted drug delivery under image guidance is gaining more interest in the drug-delivery field. ... more Targeted drug delivery under image guidance is gaining more interest in the drug-delivery field. The use of microbubbles as contrast agents in diagnostic ultrasound provides new opportunities in noninvasive image-guided drug delivery. In the present study, the imaging and therapeutic properties of novel doxorubicin liposome-loaded microbubbles are evaluated. The results showed that at scanning settings (1.7 MHz and mechanical index 0.2), these microbubbles scatter sufficient signal for nonlinear ultrasound imaging and can thus be imaged in real time and be tracked in vivo. In vitro therapeutic evaluation showed that ultrasound at 1 MHz and pressures up to 600 kPa in combination with the doxorubicin liposomeloaded microbubbles induced 4-fold decrease of cell viability compared with treatment with free doxorubicin or doxorubicin liposome-loaded microbubbles alone. The therapeutic effectiveness is correlated to an ultrasound-triggered release of doxorubicin from the liposomes and an enhanced uptake of the free doxorubicin by glioblastoma cells. The results obtained demonstrate that the combination of ultrasound and the doxorubicin liposome-loaded microbubbles can provide a new method of noninvasive image-guided drug delivery. ). c. Mannaris and M. averkiou are with the department of Mechanical and Manufacturing Engineering, University of cyprus, nicosia, cyprus. B. Geers and I. lentacker are with the laboratory

Thin solid shell contrast agents bubbles are expected to undergo different volume oscillating beh... more Thin solid shell contrast agents bubbles are expected to undergo different volume oscillating behaviors when the acoustic power is increased: small oscillations when the shell remains spherical, and large oscillations when the shell buckles. Contrary to bubbles covered with thin lipidic monolayers that buckle as soon as compressed, solid shell bubbles resist compression, making the buckling transition abrupt. Numerical simulations that explicitly incorporate a shell bending modulus give the critical buckling pressure and post-buckling shape, and show the appearance of a finite number of wrinkles. These findings are incorporated in a model based on the concept of effective surface tension. This model compares favorably to experiments when adjusting two main parameters: the buckling tension and the rupture shell tension. The buckling tension provides a direct estimation of the acoustic pressure threshold at which buckling occurs. PACS numbers: 43.25.Yw Nonlinear acoustics of bubbly liquids, 43.35.Ei Acoustic cavitation in liquids, 46.32.+x Static buckling and instability Buckling resistance of solid shell bubbles 1

The sequence proposed follows the same principle than BVM but with changes on the amplitude coeff... more The sequence proposed follows the same principle than BVM but with changes on the amplitude coefficient. Instead of sending acoustic waves with simple, double and triple bias voltage, the coefficient are equal to 1, (λ+1) and (2λ+1). Taking λ=1 gives the same coefficient than the classical BVM method.

Microbubbles, either in the form of free gas bubbles surrounded by a fluid or encapsulated bubble... more Microbubbles, either in the form of free gas bubbles surrounded by a fluid or encapsulated bubbles used currently as contrast agents for medical echography, exhibit complex dynamics under specific acoustic excitations. Nonetheless, considering their micron size and the complexity of their interaction phenomenon with ultrasound waves, expensive and complex experiments and/or simulations are required for their analysis. The behavior of a microbubble along its equator can be linked to a system of coupled oscillators. In this study, the oscillatory behavior of a microbubble has been investigated through an acousto-mechanical analogy based on a ring-shaped chain of coupled pendula. Observation of parametric vibration modes of the pendula ring excited at frequencies between 1 and 5 Hz is presented. Simulations have been carried out and show mode mixing phenomena. The relevance of the analogy between a microbubble and the macroscopic acousto-mechanical setup is discussed and suggested as an alternative way to investigate the complexity of microbubble dynamics.

Imagerie de contraste adaptative : optimisation de la fréquence d'émission. Colloque IMVIE 5 Imag... more Imagerie de contraste adaptative : optimisation de la fréquence d'émission. Colloque IMVIE 5 Imagerie pour les sciences du vivant et la médecine, Jul 2009, Mulhouse, France. HAL Id: hal-00607265 https://hal.archives-ouvertes.fr/hal-00607265

Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use... more Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles.

Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use... more Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles.

Physics Procedia, 2015

Rationale and aim: In the field of ultrasonic contrast agent imaging, Capacitive Micromachined Ul... more Rationale and aim: In the field of ultrasonic contrast agent imaging, Capacitive Micromachined Ultrasonic Transducer (cMUT) are of great interest because of their wide frequency bandwidth. However, due to their intrinsic nonlinear behaviour, their use with classical nonlinear imaging techniques (pulse inversion, amplitude modulation, harmonic imaging...) is still limited. Different approaches have been proposed to suppress the nonlinear part of the emitting signal from a cMUT. Recently, a new imaging sequence called Bias Voltage Modulation (BVM) has shown very good potential but is limited to the conventional regime of the probe (well below the collapse voltage). Thus the probe's sensitivity is not optimized. Materials and methods: An improved version of the BVM sequences is proposed to allow the use of bias voltages close to the collapse voltage. The principle is to change the coefficients associated with the successive pulses of the sequence. Experiments have been performed using a 128-element cMUT probe connected to an open scanner. For microbubbles measurements, Sonovue contrast agents have been imaged through a flow phantom. A contrast to tissue ratio (CTR) and a signal to noise ratio (SNR) were calculated to assess the efficacy of the new approach. Results: The application of BVM sequence with new coefficients show an increase of the CTR of 19 dB at high bias voltage (90% of the collapse) compared to the classical BVM sequence. Due to the high sensitivity of the probe in this regime, the SNR is also increased by 9 dB. These results reveal that the BVM sequence can be optimized further and applied at bias voltage close to the collapse and thus fully exploit the potential of the cMUT technology for contrast agent imaging.

Ultraschall in der Medizin - European Journal of Ultrasound, 2015

The subject of this study is shear stress exerted on the cell membrane by acoustic microstreaming... more The subject of this study is shear stress exerted on the cell membrane by acoustic microstreaming generated by a contrast microbubble pulsating nearby a cell. This effect is presumed to play a major role in the sonoporation process. Currently, the existing model of this effect is based on an equation that has been derived for a free hemispherical bubble resting on a rigid plane. Such a model is not adequate for an encapsulated bubble such as a contrast agent microbubble. In this study, an improved theory is suggested that assumes an encapsulated bubble to be detached from the cell membrane. The new model allows one to calculate the shear stress distribution on the cell membrane and to determine the position and the magnitude of the peak shear stress at different values of the acoustic parameters. The second problem under consideration is how to apply the model for pairwise bubble-cell interactions to bubble-cell solutions which one has to deal with in experiments. An approach is proposed to evaluate the number of cells undergoing sonoporation in a bubble-cell solution. It is shown that the reaction of a bubble-cell solution to the variation of the acoustic parameters can be different from what is expected from the analysis of pairwise interactions between single bubbles and cells. In particular, the attenuation of the driving acoustic wave caused by bubbles can considerably reduce the total efficiency of sonoporation in the solution at frequencies close to the resonance frequency of bubbles of dominant size. Numerical examples for a polydisperse bubble population are presented.

This chapter is devoted to the dynamics of encapsulated gas microbubbles which are used as contra... more This chapter is devoted to the dynamics of encapsulated gas microbubbles which are used as contrast agents and a vehicle for targeted drug delivery in medical ultrasonics. Topics covered include theoretical models describing the effect of encapsulation on the acoustic response of contrast microbubbles, models describing the interaction of contrast microbubbles with boundaries such as walls of experimental containers and blood vessels, ultrasound imaging techniques based on using microbubble contrast agents, and the phenomenon of sonoporation which is believed to open great possibilities for targeted drug delivery by means of contrast microbubbles. The chapter reviews recent results obtained in these areas.

Le développement de nouvelles technologies permettant un diagnostic précoce des cancers est essen... more Le développement de nouvelles technologies permettant un diagnostic précoce des cancers est essentiel. L'utilisation de microbulles spécifiques reconnaissant leurs cibles permet de détecter de façon sensible les sites pathologiques ciblés (e.g. tumeurs). Le but de cette analyse est de fournir une base pour des investigations de réponse acoustique des agents de contraste ciblés qui oscillent près d'une paroi imitant la paroi vasculaire. Nous proposons plus particulièrement d'utiliser un modèle de la dynamique de la bulle qui tient compte du phénomène acoustique « compression only » (Marmottant,2005). Nous allons exploiter ce phénomène pour la détection de microbulles ciblées. À cet effet, nous avons résolu l'équation d'oscillation radiale pour une bulle encapsulée à proximité d'une paroi rigide et calculer l'écho diffusé par la microbulle. En utilisant différentes conditions d'excitation et pour des microbulles de tailles différentes. L'écho en pro...