Navigator echo-based in-slice motion artifact suppression in ultrasound images based on synthetic aperture

We propose two techniques for robust motion artifact suppression in ultrasound images based on what is called navigator echoes. The navigator echo approach has been introduced and widely used in the area of magnetic resonance imaging where motion is detected along one of the image directions based on simple registration of one-dimensional projection of the image assuming rigid body motion. In ultrasound imaging, the same concept can be applied to correct for simple shifts (e.g., with linear array probes) or rotations (e.g., with convex array probes) along the width and depth direction. The first technique assumes a rigid body motion model. Hence, simple one-dimensional template matching can be used to obtain the motion parameters as in magnetic resonance imaging. Alternatively, the second technique considers a more general spatially- variant motion model. The motion parameters of this model can be obtained through localized optimization of an information theoretic criterion. The motion model parameters are then employed in the reconstruction thus providing images with substantially reduced artifacts. The proposed method was implemented on an experimental ultrasound system in which each line is obtained from 2-4 acquisitions from interleaved frames. The motion models are compared and their practical implementation for clinical systems is evaluated.