Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

Harput, Sevan; Freear, Steven; Gélat, Pierre; Saffari, Nader; Yang, Jie; Akanji, Omololu; Thomas, Peter J.; Hutchins, David A.

doi:10.1109/ultsym.2016.7728481

Cited by 2 publications

(3 citation statements)

References 18 publications

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“…Selected results presented in this paper demonstrate that when undergoing sinusoidal excitations, granular chains can propagate acoustic signals with time and frequency domain content relevant to biomedical ultrasound applications. This conclusion is substantiated by the experimental work carried out in [7].…”

Section: Discussionsupporting

confidence: 54%

“…A transduction mechanism based on the nonlinear dynamics of granular chains may in fact possess distinct features that could make it attractive to both therapeutic high-intensity focused ultrasound applications and diagnostic applications [5,6]. A recent study showed that coupling a sinusoidally excited sixbead granular chain to water could generate acoustic pressures in the form of wideband impulses, featuring spectral content close to the biomedical ultrasound frequency range [7]. Due to the complexities associated with varying the experimental parameters and also due to the metrological challenges involved in acquiring traceable acoustic pressure measurements, theoretical models capable of simulating the nonlinear transduction process have a vital role to play in understanding and optimizing the mechanisms involved.…”

Section: Introductionmentioning

confidence: 99%

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Coupling of a granular chain to an acoustic medium: Sensitivity analyses of the propagation of ultrasonic pulse trains

Gélat

Saffari

Yang

et al. 2016

2016 IEEE International Ultrasonics Symposium (IUS)

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Abstract-Effects which arise as a result of Hertzian contact between adjacent spheres of a granular chain can potentially change the nature of a signal as it propagates down the chain. The possibility thus exists of generating signals with a different harmonic content to the signal input into one end of the chain. This transduction mechanism has the potential to be of use in both diagnostic and therapeutic ultrasound applications. Due to metrological challenges which arise when characterizing this transduction process, numerical models play a fundamental role in assisting the design of these novel devices. Previously, a finite element model was presented, which predicts the acoustic pressure generated by a sinusoidally excited granular chain coupled into an acoustic medium. The study described here exploits this model to carry out sensitivity analyses of the system to key input parameters, including excitation frequency and amplitude, sphere diameter and the number of spheres present in the chain. Granular chains were excited at one end using tone burst displacement signals with fundamental frequencies of 73 kHz and 100 kHz. The final sphere of the chain was assumed to be in contact with a cylindrical vitreous carbon layer, coupled to a half-space of water. Using the finite element method, it was possible to predict the acoustic pressure in the fluid, for a specific dynamic excitation of the first sphere of the granular chain. The sensitivity analyses demonstrated that, under tone burst excitation conditions, a train of impulses could be propagated into an acoustic medium. The sensitivity analyses also show that, due to inherent nonlinearities present in this type of system, the time and frequency domain characteristics of the signals are highly sensitive to input conditions.

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Section: Discussionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Coupling of a granular chain to an acoustic medium: Sensitivity analyses of the propagation of ultrasonic pulse trains

Gélat

Saffari

Yang

et al. 2016

2016 IEEE International Ultrasonics Symposium (IUS)

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“…The developed transducer is able to transform a narrow-band sinusoidal input force into a train of wideband impulses at ultrasonic frequencies. Donahue et al [17] and Harput et al [24,25] presented the generation of ultrasound waves in water by using a granular chain with a matching layer. However, neither of these studies analyzed the energy transfer from a chain of spheres into biological tissue in detail.…”

Section: Introductionmentioning

confidence: 99%

Generation of Ultrasound Pulses in Water Using Granular Chains with a Finite Matching Layer

et al. 2017

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Wave propagation in granular chains is subject to dispersive effects as well as nonlinear effects arising from the Hertzian contact law. This enables the formation of wideband pulses, which is a desirable feature in the context of diagnostic and therapeutic ultrasound applications. However, coupling of the ultrasonic energy from a chain of spheres into biological tissue is a big challenge. In order to improve the energy transfer efficiency into biological materials, a matching layer is required. A prototype device is designed to address this by using six aluminum spheres and a vitreous carbon matching layer. The matching layer and the precompression force are selected specifically to maximize the acoustic pressure in water and its bandwidth. The designed device generates a train of wideband ultrasonic pulses from a narrow-band input with a center frequency of 73 kHz. An analytical model is created to simulate the behavior of a matching layer as a flexible thin plate clamped from the edges. This model is then verified using free-field hydrophone measurements in water, which successfully predict the increased bandwidth by generation of harmonics. The shapes of the measured and predicted waveforms are compared by calculating the normalized cross-correlation, which shows 83% similarity between both. Since the generation of harmonics is of interest in this study, the total harmonic distortion (THD) and the −6-dB bandwidth of the signals are used to analyze signal fidelity between the hydrophone measurements and the model predictions. The acoustic signals in water have a root-mean-square THD of 73%, and the model predicts a root-mean-square THD of 78%. The −6-dB bandwidths of individual pulses measured by a hydrophone and predicted with the model are 280 and 252 kHz, respectively. At these high ultrasonic frequencies, it is an experimental demonstration of resonant chains operating in water with a matching layer.

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Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

Cited by 2 publications

References 18 publications

Coupling of a granular chain to an acoustic medium: Sensitivity analyses of the propagation of ultrasonic pulse trains

Coupling of a granular chain to an acoustic medium: Sensitivity analyses of the propagation of ultrasonic pulse trains

Generation of Ultrasound Pulses in Water Using Granular Chains with a Finite Matching Layer

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