Velocity estimation using recursive ultrasound imaging and spatially encoded signals

Previously we have presented a recursive beamforming algorithm for synthetic transmit aperture focusing. At every emission a beamformed low-resolution image is added to an existing high-resolution one, and the low-resolution image from the previous emission with the current active element is subtracted yielding a new frame at every pulse emission. In this paper the method is extended to blood velocity estimation, where a new Color Flow Mapping (CFM) image is created after every pulse emission. The underlying assumption is that the velocity is constant between two pulse emissions and the current estimates can therefore be used for compensation of the motion artifacts in the data acquired in the next emission. Two different transmit strategies are investigated in this paper: (a) using a single defocused active aperture in transmit, and (b) emitting with all active transmit sub-apertures at the same time using orthogonal spatial encoding signals. The method was applied on data recorded..

Recursive Ultrasound Imaging

This paper presents a new imaging method, applicable for both 2D and 3D imaging. It is based on Synthetic Transmit Aperture Focusing, but unlike previous approaches a new frame is created after every pulse emission. The elements from a linear transducer array emit pulses one after another. The same transducer element is used after Nxmt emissions. For each emission the signals from the individual elements are beam-formed in parallel for all directions in the image. A new frame is created by adding the new RF lines to the RF lines from the previous frame. The RF data recorded at the previous emission with the same element are subtracted. This yields a new image after each pulse emission and can give a frame rate of e.g. 5000 images/sec. The paper gives a derivation of the recursive imaging technique and compares simulations for fast B-mode imaging with measurements . A low value of Nxmt is necessary to decrease the motion artifacts and to make flow estimation possible. The simulations ..