Coherence-based adaptive imaging for high-frame-rate ultrasonic imaging

Abstract

Some success has been demonstrated in the studies of adaptive imaging, but these approaches are generally not suitable for high-frame-rate imaging where broad transmit beams are required. This report introduces the signal-to-noise ratio (SNR)-dependent coherence factor (CF), which can be used for adaptive sidelobe suppression in ultrasound (US) imaging. Previous methods employed the minimum-variance-distortionless-response (MVDR)-based CF to achieve remarkable resolution improvement (by MVDR) and to suppress sidelobes (by CF). However, the SNR is often low when using an unfocused acoustic beam, giving such an approach suboptimal performance in these applications since noise also lowers the coherence and thus affects the effectiveness of the sidelobe suppression by these CF-based methods. To overcome this problem, the proposed method takes into account the local SNR in the CF formulation so that the contrast can be restored even when the SNR is low. Simulations show that the proposed method performs well even when the SNR is as low as -10 dB. Compared to the conventional CF, the contrast (CR) and contrast-to-noise ratio (CNR) in clinical US imaging can be improved, e.g., by an average of 27.2% in CR and 11.1% in CNR, with the proposed method.