Image formation and restoration using multi-element synthetic array processing

Traditionally, the number of transmit and receive processing channels is equal to the number of transducers (N) in an ultrasound imaging system. Certain applications limit the number of processing channels such that there are fewer channels than transducer elements. For these cases, a subset of M adjacent transducers-a multi-element subarray-performs echo transmission and reception. The processing channels are multiplexed across the array as beams are acquired from each of K subarrays. Combination of all subarray apertures creates a multi-element synthetic aperture (MSA) that represents the response of the entire system. Appropriate 1D filtering is applied in the spatial domain to restore a response approximating that of full phased array imaging. Compared to full phased array (FPA) imaging, MSA imaging reduces the number of front-end processing channels by a factor of N/M. Three variations of the method were simulated for a 128-element array using 32-element subarrays. The effects of the signal bandwidth, subsampling rate, and filter length on the reconstructed 2D point-spread functions are shown. The method closely approximates the performance of FPA imaging with fewer processing channels.