Performance of F-DMAS beamforming with adjustable maximum spatial lag in multi-line transmission ultrasound imaging

In Multi-Line Transmission (MLT) ultrasound imaging, high frame-rate is achieved by the simultaneous transmission of multiple focused beams along different directions. Image contrast is potentially degraded by cross-talk artifacts that, however, can be successfully attenuated e.g. by Filtered-Delay Multiply and Sum (F-DMAS) beamforming. F-DMAS is based on the computation of the autocorrelation of the aperture in reception, which is related to the spatial-coherence (SC) of backscattered signals. SC in turn is affected by the two-way beam shape. Since MLT has a major effect on SC, a new F-DMAS formulation, called Short-Lag (SL) F-DMAS, is here proposed that allows setting the maximum lag (MLAG) between the echo signals used in the correlation operation on which image reconstruction is based. The performance of the new approach in MLT imaging is assessed through simulations. Results show that the smaller the MLAG value, the better the spatial resolution and speckle uniformity. On the other hand, contrast worsens due to increasing crosstalk artifacts. This analysis thus provides valuable indications to select the MLAG (thus, a certain trade-off between contrast, resolution and speckle-SNR) based on the specific requirements for a given application.