Effects of focusing on the nonlinear interaction between two collinear finite amplitude sound beams

Tjo/tta, Jacqueline Naze; Tjøtta, Sigve; Vefring, Erlend H.

doi:10.1121/1.400523

Cited by 89 publications

(31 citation statements)

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“…Apart from the lateral beam width, the axial focal region is smaller and more pronounced than with conventional 1.5 MHz ultrasound field generation. 48 When comparing the simulation results of the beam profiles to the experimental ones ͑Figs. 6 and 7͒, in general, very similar levels occur for all four frequency components ͑ex-cept for the focal region; see below͒.…”

Section: A General Principlementioning

confidence: 99%

Self-demodulation of high-frequency ultrasound

Vos

Goertz

Jong

2010

The Journal of the Acoustical Society of America

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High-frequency (>10 MHz) ultrasound is used in, e.g., small animal imaging or intravascular applications. Currently available ultrasound contrast agents (UCAs) have a suboptimal response for high frequencies. This study therefore investigates the nonlinear propagation effects in a high-frequency ultrasound field (25 MHz) and its use for standard UCA and diagnostic frequencies (1-3 MHz). Nonlinear mixing of two high-frequency carrier waves produces a low-frequency wave, known as the self-demodulation or parametric array effect. Hydrophone experiments showed that the self-demodulated field of a focused 25 MHz transducer (850 kPa source pressure) has an amplitude of 45 kPa at 1.5 MHz in water. Such pressure level is sufficient for UCA excitation. Experimental values are confirmed by numerical simulations using the Khokhlov-Zabolotskaya-Kuznetsov equation on a spatially convergent grid.

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Section: A General Principlementioning

confidence: 99%

Self-demodulation of high-frequency ultrasound

Vos

Goertz

Jong

2010

The Journal of the Acoustical Society of America

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“…where k is the wavenumber, D is the focal length, a is the source radius, and z is the distance from the source [28]. The KZK equation was solved in the frequency domain using a finite-difference scheme that was a development of the Bergen code [29].…”

Section: B the Numerical Modelmentioning

confidence: 99%

A nonlinear propagation model-based phase calibration technique for membrane hydrophones

Cooling

Humphrey

2008

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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A technique for the phase calibration of membrane hydrophones in the frequency range up to 80 MHz is described. This is achieved by comparing measurements and numerical simulation of a nonlinearly distorted test field. The field prediction is obtained using a finite-difference model that solves the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation in the frequency domain. The measurements are made in the far field of a 3.5 MHz focusing circular transducer in which it is demonstrated that, for the high drive level used, spatial averaging effects due to the hydrophone's finite-receive area are negligible. The method provides a phase calibration of the hydrophone under test without the need for a device serving as a phase response reference, but it requires prior knowledge of the amplitude sensitivity at the fundamental frequency. The technique is demonstrated using a 50-microm thick bilaminar membrane hydrophone, for which the results obtained show functional agreement with predictions of a hydrophone response model. Further validation of the results is obtained by application of the response to the measurement of the high amplitude waveforms generated by a modern biomedical ultrasonic imaging system. It is demonstrated that full deconvolution of the calculated complex frequency response of a nonideal hydrophone results in physically realistic measurements of the transmitted waveforms.

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“…It can be found that the pressure amplitude from SBE is slightly smaller than that from KZK model in the focal region and the maximum deviation is less than 3%, but both models are in good agreement in the axial distribution and beam patterns. Moreover, previous studies [3] validated effectiveness of KZK model for a parametric focusing source. Consequently, the focused parametric model of SBE is also good valid for a parametric focusing source on a concave spherical surface with a large aperture angle in the acoustic field.…”

Section: Numerical Examplesmentioning

confidence: 99%

“…However, these works were generally used to describe nonlinear interactions of a parametric planar sound source. Although effects of focusing on the parametric interaction between two focused beams generated by monochromatic sources was investigated with KZK equation, this model is more suitable for a weak focused ultrasound beam because that it derived under the paraxial approximation and the upper limit of the applicability is about for the half aperture angle [3].…”

Section: Introductionmentioning

confidence: 99%