Real-Time Hybrid DAS/F-DMAS Blockwise Beamforming in Imaging Systems With 2-D Matrix Arrays and Embedded Microbeamformers.

The high-quality 3-D imaging can be obtained by means of densely populated 2-D matrix array probes that embed a microbeamformer ( $\mu $ BF). Delay-and-sum (DAS) beamforming is achieved by compensating for fine delays in the $\mu $ BF, and for coarse delays in the associated scanner. Modifying the operation of the $\mu $ BF integrated into the probe is really challenging, and this has discouraged the possible adoption of different beamforming algorithms. This experimental study evaluates whether the contrast and resolution benefits of the filtered-delay multiply and sum (F-DMAS) beamforming algorithm can be achieved while retaining DAS processing in the embedded $\mu $ BF and performing F-DMAS exclusively at the scanner level. Experimental tests were performed using an open scanner connected to a commercial probe equipped with a 3072-element array and an embedded DAS $\mu $ BF that reduces the channel count to 192. For this project, a simplified F-DMAS algorithm was implemented directly on the scanner. Phantom images as well as phantom and in vivo biplane movies show, for the first time, the feasibility of such a 3-D hybrid DAS/F-DMAS operation in real time. Thanks to an acquisition modality purposely developed for this project, it was possible to compare the "hybrid" images with those obtained through conventional DAS and F-DMAS, respectively. It was, thus, found that, compared with DAS, the proposed method improves both resolution [e.g., about 20% narrower point spread functions (PSFs)] and contrast [e.g., up to + 11.4-dB contrast ratio (CR)], while, compared with full F-DMAS, image quality changes to a limited extent.