Thomson's multitaper approach combined with coherent plane-wave compounding to reduce speckle in ultrasound imaging

In ultrasound imaging, the speckle pattern limits the image quality. Spatial or frequency compounding are commonly used to reduce the speckle noise or to improve the contrast. Although some recent implementations can preserve a frame rate compatible with real time imaging, most classic compounding techniques are based on the coherent combination of several radio-frequency images from the same investigated area, which reduces the frame rate. On the other hand, the Thomson’s multitaper approach aims at smoothing the speckle by incoherently combining the B-Mode images obtained after applying different apodization windows on the same original data. With only one acquisition the frame rate remains high, but the spatial resolution is decreased. In view to improve the resolution and the contrast while reducing the speckle noise, this paper proposes to combine the coherent plane wave compounding technique (CPWC) with the Thomson’s multitaper method. The resulting multitaper coherent plane wave compounding (MCPWC) takes advantage of coherent and incoherent approaches. Simulations and experimental results demonstrate that the image quality, in terms of signal-to-noise ratio, contrast and resolution, is increased using plane wave emissions at about ten steering angles with 3 Thomson’s tapers. Outside the focal area, the lateral resolution is improved by a factor 2 and the contrast by about 2 dB when compared to images obtained with a single focalization and with Thomson’s multitaper approach.