Improved resolution for ultrasound Fourier imaging

Ultrasound Fourier imaging was first initiated by Jian-yu Lu during the 90's. Using this method, one can compute an ultrasound image using a single emission, allowing a very high frame rate (up to 10000 frames per second). The main limitation of this method is the presence of geometrical artifacts, which tend to reduce the image resolution. In this study, we propose to use steered plane waves in reception instead of spherical waves as in. This helps sampling the non-null part of the ultrasound spectrum with finer resolution, while reducing the presence of artifacts. A plane wave is emitted. Back-scattered signals are measured using multiple steered plane waves. Those signals ID spectrum contain spatial information merged to create the 2D ultrasound image spectrum. Due to axial modulation, this 2D spectrum features 2 symmetric lobes. The image resolution increases when using plane waves instead of spherical waves because the sampling of these lobes is easier. The PSF size is measured both in simulation and experimentally for each method. For conventional imaging technique, this size is 155 by 311μm in axial and transverse directions. Standard Fourier imaging leads to a size of 156 by 279μm. With our spectral imaging, this size is 154μm in axial direction and 252μm in transverse direction. Using steered plane wave in a Fourier imaging framework increases the beamformed image resolution, especially in the transverse direction when compared to other beamforming methods.