Scattering by periodic cracks and theory of comb transducers

The paper presents the theoretical and experimental study of synthetic transmit aperture (STA) method combined with Golay coded transmission for medical ultrasound imaging applications. The transmission of long waveforms characterized by a particular autocorrelation function allows to increase the total energy of the transmitted signal without increasing the peak pressure. It can also improve signalto-noise ratio and increase the visualization depth maintaining the ultrasound image resolution.In the work the 128-element linear transducer array with 0.3 mm pitch excited by the 8 and 16-bits Golay coded sequences as well as a one cycle at nominal frequencies 4 MHz were used. The comparison of 2D ultrasound images of the tissue mimicking phantoms is presented to demonstrate the benefits of coded transmission. The image reconstruction was performed using synthetic STA algorithm with transmit and receive signals correction based on a single element directivity function.

Section: Resultsmentioning

confidence: 99%

Golay Coded Sequences in Synthetic Aperture Imaging Systems

Trots¹,

Tasinkevych²,

Nowicki³

et al. 2011

“…(9). Now, we need only to check if the applied wave-field solution satisfies the wave equation inside the media, which equation is represented at the plane z = 0 by the harmonic admittance G(r + nK) or more convenient, by its version g, Eq.…”

Section: Application Of Electrostatic Methodsmentioning

confidence: 99%

“…Similar electrostatic method can be applied for analyzing finite (aperiodic) system of baffles, as well (Boersma, Danicki, 1993;Danicki, 1996;Tasinkevych, 2004). Moreover, the method results in the small system of equations to be solved numerically, and yields the results which satisfy exactly the energy conservation law (with machine accuracy (Danicki, 1999;2002)), in both the generation and scattering cases.…”

Section: Introductionmentioning

confidence: 99%

Full-wave Analysis of Periodic Baffle System in Beamforming Applications

Tasinkevych¹,

Danicki²

2010

Mixed boundary-value problem for periodic baffles in acoustic medium is solved with help of the method developed earlier in electrostatics. The nice feature of the method is that the resulting matrices are relatively easy for computations and that the results satisfy exactly the energy conservation law. Illustrative numerical examples present the wave-beam steering (in the far-field) in a baffle system that may be considered as a model of one-dimensional ultrasonic transducer array.

“…This requires small interface wave damping caused by its leakage into bulk waves, in both the comb and the substrate. High damping would prevent the distant teeth contribution to the transducer output (Danicki, 2002). In this paper, weak coupling of the comb to the substrate is assumed (Quarry, Rose, 2002) applying the idle comb approximation, hence considering the surface, instead of the interface waves.…”

Section: Casementioning

confidence: 99%

“…Two most interesting cases are presented: for period of grooves smaller than half of the Rayleigh wave-length λ R , which is the case exploited in Bragg reflectors of Fabry-Perrot resonators in micro-acoustic devices (Biriukov et al, 1995;Danicki, 1984), and the case of teeth period close to λ R , applied in comb transducers (Danicki, 2002). In the latter case, the surface wave spatial frequency takes complex values for two reasons: due to the Bragg reflection and due to the scattering into bulk waves in the substrate.…”

Section: Introductionmentioning

confidence: 99%

Rayleigh Waves in an isotropic Body with Deep Periodic Grooves

Danicki¹

2010

Bragg scattering of waves propagating in a periodically disturbed substrate is widely applied in optics and micro-acoustic systems. Here, it is studied for Rayleigh waves propagating on a periodically grooved elastic substrate. Practically applied groove depth in the Bragg grating reflectors does not exceed a few percent of the Rayleigh wavelength. Here, the analysis is carried out for periodic grooves of larger depth by applying the elastic plate model for the groove walls. The computed results show that the surface wave existence and reflection depends strongly on both the groove depth and period, and that there are limited domains of both for practical applications, primarily in comb transducers of surface waves.