Novel Use of Synthetic Aperture Technique to Improve Image Quality in Ultrasound Elastography: Preliminary Investigation

Quasi-static elastography (QSE) is a well-known technique, where the ultrasound data acquired before and after a small tissue compression is analyzed to form an image, which is related to the stiffness parameter of the underlying tissue. Most studies have reported the effect of Conventional Focused Beamforming (CFB) transmit scheme on image quality of ultrasound elastography. Recently, Diverging Beam Synthetic Aperture technique (DBSAT) has been shown to improve the image quality of ultrasound images, however, very little is explored of this scheme for elastography application. This research paper presents a novel strategy to obtain better quality elastography images using the DBSAT transmit scheme. The widely used CFB technique is a line-by-line scanning technique that produces one elastogram by processing one pre- compression and one post-compression frame, however, DBSAT being a synthetic aperture approach produces several low-resolution images before summing to obtain one high resolution image. In this experimental work on tissue-mimicking phantom, we demonstrate that estimating 128 low resolution elastograms and summing them to produce one high resolution elastogram is an effective way to reduce noise and increase the elastographic image quality. More than 15dB improvement was found when comparing the image quality metrics of signal-to-noise ratio (SNR) and Contrast-to-noise ratio (CNR) from elastography images obtained from DBSAT vs. that obtained from CFB scheme.