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Acoustic cavitation has found a wide range of applications in the last few decades. For potential applications involving cavitation, the acoustic characteristics of a confocal ultrasonic setup are studied: two high-intensity focused ultrasound transducers are mounted so that their focal points overlap. A mathematical simulator is developed that takes into account nonlinear propagation, absorption, and diffraction. Each one of these physical effects is solved in the frequency domain for successive planes. Comparing the confocal setup with equivalent single transducer setups, it is shown that, with the confocal configuration, nonlinear distortion of the waveform is reduced, resulting in a greater peak rarefactional pressure and a lower peak positive pressure. Furthermore, additional features are investigated for confocal configurations such as a greater spatial stability for the focal point, which can be maintained while increasing the pressure level, and a focal region consisting of interference acting as an acoustic trap.

Stable cavitation is produced on the surface of a special target, i.e., an abrasive foil with a grain size of about 15 microm, insonified by a 473 kHz focused beam. Cavitation bubbles are first created by a pressure of about 2 MPa. Progressive reduction of the pressure to about 100 kPa leads to a state of stable cavitation characterized by strong stable emission of the half-order subharmonic. This state can be maintained for five hours if the defining parameters (position and pressure) are optimized and constant to within a few percent. There is strong evidence for the presence of "latent" cavitation bubbles, which can persist for a few minutes without being excited.

Encapsulating chemotherapeutic agents in liposomes improves targeting and efficacy of treatments against some tumors. The present work aims at evaluating if sonosensitive liposomes combined with cavitation for drug delivery enhance efficacy and reduce toxicity. Two focused beams were combined for stabilizing the cavitation cloud and an imaging probe used for guidance. Each 1MHz focused transducer had a 5cm diameter and focal length. Exposure conditions were 10.8kW/cm2 Isppa, 250Hz PRF and 1% duty cycle. Phosphatidylcholine-based nongaseous liposomes were loaded with Doxorubicin. To control for mechanical tissue damage, AT2 Dunning tumors on rats were first exposed to ultrasound only. Treatment induced temperature rose below 0.5° C. The tumor growth was not significantly slowed down by ultrasound, but histological examination of tumors evidenced large areas of necrosis which resorbed one week after ultrasound. The new liposomes were compared with conventional HSPC-based liposomes in terms of efficacy and t...

Previous in vitro studies conducted in our group have shown the feasibility of monitoring drug release from liposomes by an inertial acoustic cavitation index. We currently report in vivo experiments utilizing the cavitation index in combined treatment of AT2 Dunning tumor grafted rats with focused ultrasound and liposomal doxorubicin. Sixty‐three rats were allocated into seven groups: control, low level ultrasound treatment, high level ultrasound treatment, free doxorubicin+high level ultrasound treatment, and liposomal doxorubicin, liposomal doxorubicin+low level ultrasound treatment, and liposomal doxorubicin+high level ultrasound treatment. Based on pharmacokinetic studies, it was decided to apply ultrasound to the tumor 48 h after drug injection. An experimental setup was built to perform repeatable and rapid sonications of tumors monitored by the cavitation index. Tumor growth was assessed for a period of 35 days after tumor inoculation. Results showed that liposomal doxorubicin significantly slowed...

Drug release from liposomes can be activated by ultrasound and inertial cavitation is assumed to be the main involved mechanism. Broadband noise is known as a good indicator for such cavitation. The feasibility of assessing the extent of drug release by acoustic noise measurements has been investigated. A 1.17‐MHz focused transducer (50‐mm diameter and 50‐mm focal length) was excited with tone‐bursts (duty cycle: 10%–100%, PRF: 100 Hz–10 kHz, and Ispta < 800 W/cm2). Emitted noise was registered with a broadband needle hydrophone and bandpass filtered between the fundamental and the first harmonic frequency for assessing the instantaneous inertial cavitation activity. A cavitation index (CI) was computed by integrating the filtered signal over time. This index was validated experimentally using terephthalate oxidized to fluorescent hydroxyterephthalate under the action of free hydroxyl radicals generated by inertial cavitation. The hydroxyterephthalate fluorescence and the CI were well correlated (R2≃0.92)...

The invention relates to a device generating ultrasonic waves focused in aocal point. Said generator device comprises a plurality of transducer elements arranged externally on a support means for focusing into a focal point, such as a circular dome, and is characterized in that the transducer elements are divided into at least two groups of transducer elements, of which the resonance frequency differs in such a way that the principal positive ultrasonic waves produced by each group add up together and the positive and negative secondary ultrasonic waves are at least partly cancelled, thus reducing significantly the negative waves. This device can be advantageously used for extracorporeal lithotripsy.

An apparatus for generating high frequency shock waves having a truncated ellipsoidal reflector is provided. The apparatus has a cavity which constitutes a chamber for reflecting shock waves, the chamber being filled with a dielectric liquid such as water or oil. The apparatus also has a shock wave generator device which generally has two electrodes and a source for selectively and substantially instantaneously providing an electric voltage to the electrodes. The equipotential screen is fast with the ellipsoidal reflector and is grounded by the support formed by the ellipsoidal reflector. This equipotential screen limits electric leakage and thus renders the apparatus safer in operation for destroying targets such as tissues, biliary concretions, kidney stones, etc.