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The new application of ultrasonic imaging to transient elastography has triggered the emergence of high frame-rate imaging. Using plane wave excitation (PWE), a single insonification is sufficient to form an image; thus PWE is one of the methods for achieving high frame-rate imaging. However, due to the lack of transmit focusing, the signal-to-noise-ratio (SNR), contrast, and spatial resolution of...
A 2-D slot array structure to achieve near-field beam focusing, with a linear polarization, is proposed and demonstrated using full-wave simulations. The proposed structure has a negligible cross-polarization and its far-field gain is lower by 10 dB compared to the non-focus case, indicating a good focusing in the near-field of the structure.
Recently, a wide spectrum of new applications in biomedical ultrasound such as real time 3D ultrasound and transient elastography has triggered the need of high frame-rate imaging. One of the methods to achieve high frame-rate imaging is to use plane wave excitation (PWE) with which a single insonification is sufficient to form an image. However, due to the lack of transmit focusing, the signal-to-noise-ratio...
Speckle tracking is capable of searching the complete vector velocity but is susceptible to the frame-to-frame image de-correlation. With plane-wave excitation (PWE), the high frame-rate reduces the scatterer displacement and thus increases the signal correlation. Nevertheless, the lower image quality with PWE may suffer from spatial velocity gradient outside the sample volume and reduce the achievable...
Sidelobe contribution from off-axis scatterers degrades image quality in ultrasound imaging. Focusing errors resulting from sound-velocity inhomogeneities in tissues, also known as phase aberrations, reduce coherence of the received signals and thus elevates the sidelobe level degrading the contrast resolution. In this study, we proposed a novel adaptive sidelobe-reduction technique using aperture...
Synthetic aperture focusing using a virtual source was used previously to increase the penetration and to extend the depth of focus in high-frequency ultrasonic imaging. However, the performance of synthetic aperture focusing is limited by its high sidelobes. In this paper, an adaptive weighting technique based on a focusing-quality index is introduced to suppress the sidelobes. The focusing-quality...
Sound-velocity inhomogeneities degrade both spatial and contrast resolutions. This paper proposes a new adaptive imaging technique that uses the generalized coherence factor (GCF) to reduce the focusing errors resulting from the sound-velocity inhomogeneities. The GCF is derived from the spatial spectrum of the received aperture data after proper receive delays have been applied. It is defined as...
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