Mechanisms for saturation of nonlinear pulsed and periodic signals in focused acoustic beams

Karzova, Maria M.; Averiyanov, Mikhail; Sapozhnikov, Oleg A.; Khokhlova, Vera A.

doi:10.1134/s1063771011060078

Cited by 26 publications

(19 citation statements)

References 8 publications

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“…To produce comparable and clinically relevant acoustic pulse energies in an area surrounding the target stone, the new lens must operate at a higher source voltage (i.e., 16-19 kV) than the one used for the original lens (i.e., 13-16 kV) to compensate for the acoustic energy loss caused by destructive in situ pulse superposition. However, significant prefocal shift in p + will occur at high output voltages owing to nonlinear wave propagation (25,26).…”

Section: Resultsmentioning

confidence: 99%

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

Neisius

Smith

Sankin

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The efficiency of shock wave lithotripsy (SWL), a noninvasive firstline therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E + ) of 40 mJ. The −6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters. electromagnetic lithotripter | lens modification | stone fragmentation

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Section: Resultsmentioning

confidence: 99%

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

Neisius

Smith

Sankin

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…[49][50][51] A method of fractional steps with an operator splitting procedure was used to march the solution over the axial coordinate z. A combined time and frequency domain solution was used.…”

Section: B Measurement Protocols and Pulse Definitionsmentioning

confidence: 99%

Acoustic field characterization of the Duolith: Measurements and modeling of a clinical shock wave therapy device

Perez

Chen

Matula

et al. 2013

The Journal of the Acoustical Society of America

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Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from -2 to -11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabolotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled.

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“…14,15 Two of them, the source physical characteristics and the wave velocity in the medium, can be described through a single parameter, the Fresnel number. This parameter, defined as N F ¼ a 2 /kF, where a is the transducer radius, k the wavelength, and F the geometrical focal length, is widely used in optics and allows classifying the sound beams according to low (N F $ 1) or high (N F > 1) focusing degree.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear focal shift beyond the geometrical focus in moderately focused acoustic beams

Camarena

Adrián-Martínez

Jiménez

et al. 2013

The Journal of the Acoustical Society of America

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The phenomenon of the displacement of the position along the axis of the pressure, intensity, and radiation force maxima of focused acoustic beams under increasing driving voltages (nonlinear focal shift) is studied for the case of a moderately focused beam. The theoretical and experimental results show the existence of this shift along the axis when the initial pressure in the transducer increases until the acoustic field reaches the fully developed nonlinear regime of propagation. Experimental data show that at high amplitudes and for moderate focusing, the position of the on-axis pressure maximum and radiation force maximum can surpass the geometrical focal length. On the contrary, the on-axis pressure minimum approaches the transducer under increasing driving voltages, increasing the distance between the positive and negative peak pressure in the beam. These results are in agreement with numerical KZK model predictions and the existed data of other authors and can be explained according to the effect of self-refraction characteristic of the nonlinear regime of propagation.

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Mechanisms for saturation of nonlinear pulsed and periodic signals in focused acoustic beams

Cited by 26 publications

References 8 publications

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

Acoustic field characterization of the Duolith: Measurements and modeling of a clinical shock wave therapy device

Nonlinear focal shift beyond the geometrical focus in moderately focused acoustic beams

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