An efficient subarray average delay multiply and sum beamformer algorithm in ultrasound imaging

Beamformer plays an important role in medical ultrasound imaging systems. The delay multiply and sum (DMAS) beamformer achieves better performance in contrast and resolution compared with the delay and sum (DAS) beamformer, but suffers from higher computational complexity and partial energy loss. The higher computational complexity mainly arises from the multiply and geometric average operation, which needs (N²-N)/2 computations at every point, where N denotes the number of array elements. The partial energy loss, mainly due to the autocorrelation component of the echo signals, has been neglected in the DMAS beamformer. In this paper, we propose a subarray average delay multiply and sum (SA-DMAS) beamformer which is combined with subarray average technique of covariance matrix and DMAS beamformer. This will lower the computational complexity, while keeping the side lobe suppressing property of DMAS. The main idea of the proposed method is adding autocorrelation component of the echo signals to DMAS, and converting the expression in covariance matrix form. The subarray average technique is used to estimate the covariance matrix of the echo signals. The field II simulation of point targets and cyst phantoms was used to prove the performance of the proposed method. An RF data experiment was applied to support the feasibility and validity of our method. The simulation and experimental results show that our method has a lower computational complexity as O(9/2L²) , where L denotes the sub-array size, and has equivalent performance like the MV and DMAS beamformer.