Encoded multiple simultaneous aperture acquisition for improved signal-to-noise ratio in ultrasound imaging

摘要

Here, we propose a new technique that allows the improvement of SNR without lowering the frame rate. The basic version of the proposed technique works by exciting multiple non-overlapping apertures at the same time. Assuming N apertures are to be acquired simultaneously, N acquisitions from such arrangement are made with different aperture coding in each acquisition. In particular, the excitation to each aperture is multiplied by a different predetermined factor for each acquisition. By properly selecting these factors, the problem of estimating the different lines become equivalent to solving a well-conditioned linear system of size N. Also, we show that such factors can be chosen to make the system matrix orthogonal, thus enabling simple solution to be obtained. We describe the implementation of such procedure and demonstrate that it is possible to achieve in practice even for systems in which the sign of excitation can only be changed. For more advanced system where coded excitations can be used, more accurate implementation taking into account element sensitivity variations within each probe for closer adherence to the desired characteristics. The proposed system results in noise reduction that is equivalent to averaging N acquisitions similar to phase encoding in magnetic resonance imaging. At the same time, the system maintains the same lateral resolution and frame rate as conventional acquisition strategies. We also discuss the use of sub-optimal overlapped apertures and describe the deterioration of SNR gain as a result of using independent rather than orthogonal apertures.