Phase-inversion-based selective harmonic elimination (PI-SHE) in multi-level switched-mode tone- and frequency- modulated excitation

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

Arif

McLaughlan

et al. 2013

Self Cite

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.

Section: Discussionmentioning

confidence: 99%

The effect of amplitude modulation on subharmonic imaging with chirp excitation

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

Arif

McLaughlan

et al. 2013

Self Cite

“…This laser light was applied on the phantom through a optical fibre that its output diameter is 2 mm (NA = 0.22). The generated photoacoustic emissions were recoded by using Ultrasound Array Research Platform II (UARP II) [11], [12] centre frequency 7.5 MHz and a bandwidth(-6 dB) 90 % . The linear array transducer was moved in the elevation direction by using stepper motor (Zolix, PSA 100-11-X) with step size of 0.1 mm.…”

Section: B Fdmas Beamforming Techniquementioning

confidence: 99%

Elevation resolution enhancement in 3D photoacoustic imaging using FDMAS beamforming

Alshaya

2017 IEEE International Ultrasonics Symposium (IUS)

Cowell

et al. 2017

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Abstract-Photoacoustic imaging is a non-invasive and nonionizing imaging technique that combines the spectral selectivity of laser excitation with the high resolution of ultrasound imaging. It is possible to identity the vascular structure of the cancerous tissue using this imaging modality. However, elevation and lateral resolution of photoacoustic imaging is usually poor for imaging target. In this study, three dimension filter delay multiply and sum beamforming technique (FDMAS(3D)) is used to improve the resolution and enhance the signal to noise ratio (SNR) of the 3D photoacoustic image that is created by using linear array transducer. This beamforming technique showed improvement in the elevation by 36% when its compared with three dimension delay and sum beamforming technique (DAS(3D)). In addition, it enhanced the SNR by 13 dB compared with DAS (3D).

“…Diluted SonoVue R microbubble solution with a clinically relevant concentration was driven by a syringe pump (Aladdin AL-1000, World Precision Instruments) with a constant volume rate of 24 ml/minute. [14], [15] which is capable of providing arbitrary excitation schemes, and ultrafast PWI at 500 Hz was acquired by firing all the 128 elements of the linear transducer array with negative excitation pulse controlled by the Leeds UARP II.…”

Section: Materials and Experimentsmentioning

confidence: 99%

Velocity estimation error reduction in stenosis areas using a correlation correction method

Nie

2016 IEEE International Ultrasonics Symposium (IUS)

Cowell

et al. 2016

Self Cite

Abstract-The advent of ultrafast ultrasound imaging proved beneficial for capturing transient flow patterns which was never readily achievable before. Velocity estimation methods based on 2D block-matching outperform Doppler based methods by offering higher frame rate with the cost of increased uncertainty in presence of out-of-plane motion as a result of turbulent flow.Local median filtering can partially address the estimation error reduction in stenosis areas at the risk of higher inaccuracy, since neighboring values may be also outliers. In this study, a correlation correction method is proposed, where the out-of-plane motion is eliminated by means of multiplying correlation maps from a same area but in two adjacent pairs of RF images.Experimental investigations were performed on a wall-less flow phantom, and proposed method achieved an error reduction of 66% in turbulent flow regions.