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Source Density Apodisation: Image Artefact Suppression through Source Pitch Non-Uniformity

Alles, EJ; Desjardins, AE; (2019) Source Density Apodisation: Image Artefact Suppression through Source Pitch Non-Uniformity. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 10.1109/tuffc.2019.2945636. (In press). Green open access

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Abstract

Conventional ultrasound imaging probes typically comprise finite-sized arrays of periodically spaced transducer elements, which in the case of phased arrays can result in severe grating and side lobe artefacts. Whereas side lobes can be effectively suppressed through amplitude apodisation (“AmpA”), grating lobes arising from periodicity in transducer placement can only be suppressed by decreasing the element pitch, which is technologically challenging and costly. In this work, we present source density apodisation (“SDA”) as an alternative apodisation scheme, where the spatial source density (and hence the element pitch) is varied across the imaging aperture. Using an all-optical ultrasound imaging setup capable of video-rate 2D imaging as well as dynamic and arbitrary reconfiguration of the source array geometry, we show both numerically and experimentally how SDA and AmpA are equivalent for large numbers of sources. For low numbers of sources, SDA is shown to yield superior image quality as both side and grating lobes are effectively suppressed. In addition, we demonstrate how asymmetric SDA schemes can be used to locally and dynamically improve the image quality. Finally, we demonstrate how a non-smoothly varying spatial source density (such as that obtained for randomised arrays or in the presence of source positioning uncertainty or inaccuracy) can yield severe image artefacts. The application of SDA can thus yield high image quality even for low channel counts, which can ultimately result in higher imaging frame rates using acquisition systems of reduced complexity.

Type: Article
Title: Source Density Apodisation: Image Artefact Suppression through Source Pitch Non-Uniformity
Open access status: An open access version is available from UCL Discovery
DOI: 10.1109/tuffc.2019.2945636
Publisher version: https://doi.org/10.1109/tuffc.2019.2945636
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Ultrasonic imaging, Apertures, Optical imaging, Optical sensors, Transducers, Detectors
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10082960
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