On the Use of the Geometric Median in Delay-and-Sum Ultrasonic Array Imaging

Abstract

Delay-and-sum algorithms are imaging techniques in non-destructive testing which form images by summing backpropagated signals. Under this approach, a small number of high intensity signals, such as those from boundary reflections, may create artefacts which degrade the image and hinder defect detection. This paper introduces a probabilistic model of the summation which explains the origin of this effect and proposes to replace the summation in the imaging algorithm by the more statistically robust geometric median. As demonstrated on a experimental inspection using multi-view Total Focusing Method and Plane Wave Imaging, this novel technique effectively suppresses some artefacts, at the expense of an increase of the structural noise amplitude and additional diffraction artefacts at the ends of some structural features. As such the geometric median provides an alternative imaging approach that may improve performance in some circumstances.

Ultrasonic Image Artifacts Removing Technique Based on SoS Kernel

“…Moreover, Potter [14] et al proposed a technique to reduce the artifacts using a hybrid full matrix formed through a temporally weighted sum of coherent and reconstructed matrices. In addition, Huthwaite [15] proposed a method combined with weighting function filtering and the truncation imaging algorithm to eliminate the artifacts, and Budyn [16] adopted a statistical robustness geometry mid-value to replace the delay-superposition imaging algorithm for suppressing the artifacts. In 2019, Guanru [17] generated a phase reversal signal to counteract the signal tail.…”