Minimum variance beamforming using fine pitch array probe with limited aperture size

Recent studies have reported the advantageous aspects of minimum variance beamforming (MVBF) such as an improvement in main lobe resolution and clutter level reduction. Unlike a conventional delay-and-sum beamformer (DASBF) that suffers from a degradation in resolution when the aperture size is limited, MVDF can cope with it. However, the covariance matrix dimension is also reduced resulting in low performance of MVBF. Moreover, spatial smoothing processing in MVBF also reduces the covariance matrix dimension. To overcome this problem, we herein propose a fine pitch array whose number of elements is increased using the same aperture size. Although this method requires more computation, it maximizes the performance of MVBF. The efficacy of the proposed method is verified by constructing and comparing images from pulse echo data using Field II simulation as well as from experimental data on a real tissue mimicking phantom.