  In Ultrasound (US) imaging, Delay and Sum (DAS) is the most common
beamformer, but it leads to low quality images. Delay Multiply and Sum (DMAS)
was introduced to address this problem. However, the reconstructed images using
DMAS still suffer from level of sidelobes and low noise suppression. In this
paper, a novel beamforming algorithm is introduced based on the expansion of
DMAS formula. It is shown that there is a DAS algebra inside the expansion, and
it is proposed to use DMAS instead of the DAS algebra. The introduced method,
namely Double Stage DMAS (DS-DMAS), is evaluated numerically and
experimentally. The quantitative results indicate that DS-DMAS results in about
25% lower level of sidelobes compared to DMAS. Moreover, the introduced method
leads to 23%, 22% and 43% improvement in Signal-to-Noise Ratio,
Full-Width-Half-Maximum and Contrast Ratio, respectively, in comparison with
DMAS beamformer.
