Covariance Matrix based Coherence Beamforming Strategies in Medical Ultrasound

As we known that conventional beamforming strategy, delay and sum, (DAS) does not have excellent resolution, contrast and off-axial signal suppression. Therefore, we introduce coherence measurement to beamforming strategy to improve performance of that. We analyze convolutional beamforming algorithm (COBA) and DAS from views of covariance matrix and find that COBA could be regarded as the square root of Covariance Matrix based Phase Coherence Factor (CMPMCF) and proposed novel covariance matrix based coherence strategies. Furthermore, combined CMPMCF with sparse array designing, we propose sparse CMPMCF for purpose that reducing the number of receiving channels while performance of sparse CMPMCF as same as that of DAS. These proposed covariance matrix based coherence beamforming strategies has been assessed via simulation and phantom experimental datasets. The results shows that the square root of CMPMCF is equivalent to COBA, also achieving similar image enhancement effect. Besides sparse CMPMCF could obtain similar performance with that of DAS while the number of receiving channel significantly reduced.