Synthetic transmit beam steering for spatial compounding applications using continuous transmit focusing

Traditional spatial compounding, in general, employs multiple distinct transmit/receive beam angles which insonify a common region, from which multiple images are formed. The individual images are detected, resampled onto a common grid, and combined in order to produce better image quality, whose attributes are better contrast resolution, reduced speckle, reduced shadowing artifacts, and better borders. However, the increase in image quality comes at a cost in increased acoustic acquisition time, with a corresponding drop in frame rate. Combination modes such as B+CD places heavy demands on acquisition time, and in order to maintain adequate frame rates, the number of B-mode spatial compounding views is reduced or eliminated when in CD-mode, reducing B-mode image quality. In order to provide spatial compounding while maintaining the same acoustic acquisition time, multiple steered transmit beams are synthesized from the same set of channel data acquired for the non-steered view, using a continuous transmit focusing technique.