Electronic beam steering of shock waves

Cathignol, D.; Birer, Alain; Nachef, Sylvain; Chapelon, Jean‐Yves

doi:10.1016/0301-5629(94)00115-t

Cited by 20 publications

(6 citation statements)

References 11 publications

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“…To date, the primary focus of customizing the acoustic field has been to electronically steer the focus to track the kidney stone during treatment. 20,21 Both studies employed a spherical transducer array with high voltage pulser circuits for each individual element and achieved efficient focusing in an ellipsoidal region of about 4 cm in diameter and 6 cm in length. The present work employs a similar spherical transducer and pulse generator system to customize spatial pressure distribution.…”

Section: Introductionmentioning

confidence: 99%

Customization of the acoustic field produced by a piezoelectric array through interelement delays

Chitnis

Barbone

Cleveland

2008

The Journal of the Acoustical Society of America

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A method for producing a prescribed acoustic pressure field from a piezoelectric array was investigated. The array consisted of 170 elements placed on the inner surface of a 15 cm radius spherical cap. Each element was independently driven by using individual pulsers each capable of generating 1.2 kV. Acoustic field customization was achieved by independently controlling the time when each element was excited. The set of time delays necessary to produce a particular acoustic field was determined by using an optimization scheme. The acoustic field at the focal plane was simulated by using the angular spectrum method, and the optimization searched for the time delays that minimized the least squared difference between the magnitudes of the simulated and desired pressure fields. The acoustic field was shaped in two different ways: the −6 dB focal width was increased to different desired widths and the ring-shaped pressure distributions of various prescribed diameters were produced. For both cases, the set of delays resulting from the respective optimization schemes were confirmed to yield the desired pressure distributions by using simulations and measurements. The simulations, however, predicted peak positive pressures roughly half those obtained from the measurements, which was attributed to the exclusion of nonlinearity in the simulations.

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Section: Introductionmentioning

confidence: 99%

Customization of the acoustic field produced by a piezoelectric array through interelement delays

Chitnis

Barbone

Cleveland

2008

The Journal of the Acoustical Society of America

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“…The main sources of uncertainty in our measurements are: pressure-averaging effect over the surface of the hydrophone active element, error in the measured value of the shockwave hydrophone sensitivity, 36 and error in the measurement of the generator electro-acoustical conversion factor at its source surface. 30,37 Among these, we believe that the first one, i.e., the effect of pressure averaging over the surface of hydrophone active element, has had the most important influence on our measurements, especially in nonlinear regime when the focus dimensions become comparable with, or even smaller than, the hydrophone active element size (⌽ϭ1 mm in our measurements͒. To obtain an idea of the influence of this averaging effect on our results, we made a simple simulation in nonlinear regime and in water.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Modeling of pulsed finite-amplitude focused sound beams in time domain

Tavakkoli

Cathignol

Souchon

et al. 1998

The Journal of the Acoustical Society of America

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107

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A time-domain numerical model is presented for simulating the finite-amplitude focused acoustic pulse propagation in a dissipative and nonlinear medium with a symmetrical source geometry. In this method, the main effects responsible in finite-amplitude wave propagation, i.e., diffraction, nonlinearity, and absorption, are taken into account. These effects are treated independently using the method of fractional steps with a second-order operator-splitting algorithm. In this method, the acoustic beam propagates, plane-by-plane, from the surface of a highly focused radiator up to its focus. The results of calculations in an ideal (linear and nondissipative) medium show the validity of the model for simulating the effect of diffraction in highly focused pulse propagation. For real media, very good agreement was obtained in the shape of the theoretical and experimental pressure-time waveforms. A discrepancy in the amplitudes was observed with a maximum of around 20%, which can be explained by existing sources of error in our measurements and on the assumptions inherent in our theoretical model. The model has certain advantages over other time-domain methods previously reported in that it: (1) allows for arbitrary absorption and dispersion, and (2) makes use of full diffraction formulation. The latter point is particularly important for studying intense sources with high focusing gains.

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“…In our laboratory, a new shock-wave generator was developed to achieve focused tissue destruction by shock waveinduced cavitation [ 19], [20]. For the field characterization of this generator (particularly at the focal region) we have used the different kinds of commercially available hydrophones which are applicable for shock wave measurements, including PVDF bilaminar shielded membrane and PVDF needle hydrophones.…”

Section: Physical Parameters Of the Shock-wave Fieldsmentioning

confidence: 99%

“…During the past few years, a series of shock-wave generators for lithotripsy and/or tissue destruction studies has been developed in our laboratory [19], [20]. The last version of them that was used in this study is a piezoelectric generator with electronic focusing capability.…”

Section: A Shock-wave Generatormentioning

confidence: 99%

Development of a PVDF low-cost shock-wave hydrophone

1996

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Abstract. During a few past years a series of shock-wave generators for lithotripsy and/or tissue destruction studies have been developed in our laboratory. Based on the experiences in shock wave measurements and the drawbacks in existing hydrophones, we have developed a very low-cost, wideband, reproducible shock-wave hydrophone. The key element of this device is the rapidly mounting, disposable PVDF membrane. This is a commercially available PVDF shock gauge which is poled by a patented cyclic poling technique. To obtain the widest possible bandwidth, we have adopted a special coplanar membrane design. The PVDF film is sandwiched between the surfaces of a P.V.C. and a metallic plate of brass which the latter is in contact with the surrounding medium. On the other hand, the active lead is isolated from medium and it is in contact with an isolating liquid (degassed petroleum) held in a cylindrical chamber over the membrane. By the incorporation of this design, the hydrophone can be used for shock wave measurements even in conductive media like different physiological liquids, with a negligible change of sensitivity.

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Electronic beam steering of shock waves

Cited by 20 publications

References 11 publications

Customization of the acoustic field produced by a piezoelectric array through interelement delays

Customization of the acoustic field produced by a piezoelectric array through interelement delays

Modeling of pulsed finite-amplitude focused sound beams in time domain

Development of a PVDF low-cost shock-wave hydrophone

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