Spectral Doppler analysis with sparse and full 2-D arrays

Sparse arrays represent an alternative to full-gridded arrays in 2-D probes realization. Sparse arrays have been used in B-mode imaging tests, but not in spectral Doppler measurements yet. In this paper, we have investigated, by mean of simulations and experiments, how the use of a sparse array instead of a full-gridded 2-D array impacts on spectral Doppler measurements. A 3 MHz, 1024-element gridded array and a sparse array obtained by properly selecting 256 elements from the full array, have been used to interrogate a parabolic flow. Simulations and experiments highlight that the mean Doppler frequency does not change by using the sparse array instead of the full one. Significant differences appear for the bandwidth (17.2% average bandwidth reduction for the sparse array), and for the signal power (22 dB). Possible explanations of this behavior are discussed. Furthermore, it is shown that the empty lines in the 2-D array impact on the Doppler spectra, leading to sidelobes when steering in the direction perpendicular to such lines.