SNR-dependent filter design for improving depth of field

Conventional ultrasound systems with fixed transmit focus and dynamic receive focusing suffer from limited depth of field and poor SNR uniformity. Based on fixed receive focusing, this paper proposes an SNR-dependent 2-D retrospective filtering technique to extend the depth of field, in which both the sidelobe energy and the filter energy are minimized simultaneously. According to the estimated SNR of the unfiltered image, the proposed 2D filter can provide the optimal compromise between image quality and SNR while maintaining the moderate filter size. Simulations were performed to demonstrate the efficacy of the proposed technique. It has been shown that the proposed 2-D filter technique outperforms conventional 1-D lateral filter and classical 2-D Wiener filter in terms of both SNR and contrast resolution.