Experimental investigation of the subharmonic emission from microbubbles using linear and nonlinear frequency modulated signals

Harput, Sevan; Arif, Muhammad; Freear, Steven

doi:10.1109/ultsym.2010.5935909

Cited by 4 publications

(6 citation statements)

References 14 publications

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“…The excitation center frequency was selected as 7.6 MHz, since it was double the resonance frequency of the microbubbles used in this study. Instead of comparing the peak subharmonic power or subharmonic-to-fundamental ratio, which are commonly used for characterizing microbubbles and for measuring their nonlinear behaviors [48], [50], [51], the total subharmonic power was calculated to evaluate the subharmonic behavior of UCAs to different excitation signals. The reason for using this method was due to the variation in bandwidths of the LFM and NLFM chirps used in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Increasing the excitation bandwidth of a fixed duration signal was spread the signal's energy to a wider spectral range and increased the likelihood of subharmonic generation from a polydisperse population of microbubbles [48]. Increasing the signal's total energy by using a different amplitude modulation also improves the subharmonic response from UCAs.…”

Section: A Subharmonic Generation With Lfm and Nlfmmentioning

confidence: 99%

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The effect of amplitude modulation on subharmonic imaging with chirp excitation

Harput

Arif

McLaughlan

et al. 2013

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

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Abstract-Subharmonic generation from ultrasound contrast agents depends on the spectral and temporal properties of the excitation signal. The subharmonic response can be improved by using wideband and long duration signals. However, for sinusoidal tone-burst excitation the effective bandwidth of the signal is inversely proportional with the signal duration. Linear frequency modulated (LFM) and nonlinear frequency modulated (NLFM) chirp excitations allow independent control over the signal bandwidth and duration, therefore in this study LFM and NLFM signals were used for the insonation of microbubble populations. The amplitude modulation of the excitation waveform was achieved by applying different window functions. A customized window was designed for the NLFM chirp excitation by focusing on reducing the spectral leakage at the subharmonic frequency and increasing the subharmonic generation from microbubbles.Subharmonic scattering from a microbubble population was measured for various excitation signals and window functions. At a peak-negative pressure of 600 kPa, the generated subharmonic energy by ultrasound contrast agents was 15.4 dB more for NLFM chirp excitation with 40% fractional bandwidth when compared to tone-burst excitation. For this reason, the NLFM chirp with a customized window was used as an excitation signal to perform subharmonic imaging in an ultrasound flow phantom. Results showed that the NLFM waveform with a customized window improved the subharmonic contrast by 4.35 ± 0.42 dB on average over a Hann windowed LFM excitation.

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Section: Discussionmentioning

confidence: 99%

Section: A Subharmonic Generation With Lfm and Nlfmmentioning

confidence: 99%

The effect of amplitude modulation on subharmonic imaging with chirp excitation

Harput

Arif

McLaughlan

et al. 2013

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

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“…Nevertheless, out of the presented nonlinear methods, many research works demonstrated the benefit of subharmonic analysis when microbubbles, therefore porosity, are considered [ 53 , 65 , 66 , 67 , 68 , 69 , 70 ]. A generic amplitude spectrum of an acquired filtered backscattered signal can be presented as shown in Figure 3 .…”

Section: Nonlinear Ultrasound Approachmentioning

confidence: 99%

“…Among them, nonlinear elastic wave spectroscopy (NEWS) [ 40 , 41 , 42 ], nonlinear elastic wave modulation spectroscopy (NEWMS) [ 43 , 44 , 45 ], nonlinear imaging methods [ 46 , 47 , 48 ], and phase symmetry analysis (PSA) techniques [ 49 , 50 ] were used to explicitly interrogate the nonlinear behaviour of the medium and its effect on wave propagation. Many studies have shown that nonlinearities are generated in structures in the presence of ruptures, voids, cohesive bonds, and the opening/closing of surfaces or micro-cracks [ 51 , 52 , 53 ]. Material nonlinearity of damaged regions, in terms of nonlinear harmonic generation (due to ultrasound excitation), has been widely used over the past few years as a reliable signature for material flaw detection in both metallic and composite structures [ 46 , 54 , 55 ].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Ultrasonic Imaging for Porosity Evaluation

Simone

Boccardi

Fierro

et al. 2023

Sensors

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The influence of porosity on the mechanical behaviour of composite laminates represents a complex problem that involves many variables. Therefore, the evaluation of the type and volume content of porosity in a composite specimen is important for quality control and for predicting material behaviour during service. A suitable way to evaluate the porosity content in composites is by using nonlinear ultrasonics because of their sensitivity to small cracks. The main objective of this research work is to present an imaging method for the porosity field in composites. Two nonlinear ultrasound techniques are proposed using backscattered signals acquired by a phased array system. The first method was based on the amplitude of the half-harmonic frequency components generated by microbubble reflections, while the second one involved the frequency derivative of the attenuation coefficient, which is proportional to the porosity content in the specimen. Two composite samples with induced porosity were considered in the experimental tests, and the results showed the high accuracy of both methods with respect to a classic C-scan baseline. The attenuation coefficient results showed high accuracy in defining bubble shapes in comparison with the half-harmonic technique when surface effects were neglected.

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“…therefore, care must be taken in choosing the optimum number of cycles). In addition this technique combined with nonlinear frequency modulated ultrasound signals (Harput et al 2010) will further improve the signal to noise and resolution.…”

Section: Possible Applications Of the Observed Phenomenonmentioning

confidence: 99%

Numerical and experimental investigation of the dynamics of ultrasound contrast agents excited at higher multiples of their natural resonance frequency

Sojahrood¹

2021

Preprint

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In this work the Hoff model for microbubble oscillations was used together with bifurcation diagrams to investigate microbubble behavior for a range of the system control parameters (driving frequency and pressure, microbubble size and shell parameters). We have shown that if the microbubble sizes are optimized so that their resonance frequency is a fraction of the sonication frequency (1/3, 1/4...), above a certain pressure threshold, the microbubbles can emit higher order subharmonics at (1/3, 2/3...) of the sonication frequency. Experimental results (using Artenga and in-house made lipid microbubbles with a 25 MHz, 30 cycle pulse using 0.1-2.5 MPa pressures) showed subpopulations of the microbubbles that were able to show this behaviour by scattering ultrasound according to the theoretical predictions (e.g. having two frequency maxima for subharmonics at f/3 and 2f/3). The ring-down analysis of the natural free oscillations of these microbubbles confirmed the theoretical resonance predictions.

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Experimental investigation of the subharmonic emission from microbubbles using linear and nonlinear frequency modulated signals

Cited by 4 publications

References 14 publications

The effect of amplitude modulation on subharmonic imaging with chirp excitation

The effect of amplitude modulation on subharmonic imaging with chirp excitation

Nonlinear Ultrasonic Imaging for Porosity Evaluation

Numerical and experimental investigation of the dynamics of ultrasound contrast agents excited at higher multiples of their natural resonance frequency

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