Reducing Grating Lobe Artifacts by Exploiting Lateral Transducer Motion

Abstract

Grating lobes (GL) are the consequence of the lateral spatial undersampling in terms of too large pitch values of ultrasound transducer array elements with respect to the center frequency. It is well known that GLs can be eliminated if the pitch, i.e. the inter-element distance, is set to half of the wavelength. In case the emitted acoustic wave is not steered but send out perpendicular to the transducer array, a pitch equal to the full wavelength is sufficient to eliminate GLs. However, due to manufacturing limits a pitch that avoids GLs is not always feasible especially if high frequency transducers are used. On receive, GLs reveal themselves as regions with an unintended high sensitivity next to the focal point. On transmission, GLs show up as regions with impeding high-pressure intensities next to the main lobe. In the ultrasound image, GLs are responsible for lateral mispositioning of structures resulting in a clouding effect that reduces image contrast. In this contribution, we present an approach that suppresses GL artifacts by exploiting lateral transducer motion. The approach is intended for plane wave imaging with linear array transducers that have a pitch larger than half of the wavelength. The proposed technique is based on a spatial compounding of data acquired with a synthetic receive aperture that can be computed by incorporation of lateral transducer-tissue-displacement.