|
In the conventional digital ultrasound scanner, the reflected signal is sampled either in polar coordinates of R-θ method, or in Cartesian coordinates of uniform ladder algorithm (ULA). The R-θ scan method necessitates a coordinate transform process which makes hardware complex in comparison with ULA scan mrthoA In spite of this complexity, R-θ method has a good resolution in ultrasonographic (US) image, since scan direction of the US imaging is a radial direction. In this paper, a new digital scan converter is proposed, which is named the radius uniform ladder algorithm (RULA). The RULA has the rome scan direction as the US scanning in the radial direction and as the display space in the θ direction. In tllis new approach, sampled points we uniformly distributed in each horizontal line i.n well as in each radial ray so that the data are displayed in the Cartesian coordinates by the 1-D interpolation process. The propped algorithm has an uniform resolution in the periphery and the center field in comparison with equi-angle ULA and equi-interval ULA. To extend the scan angle, concentric square raster sampling (CSRS) is adopted with reduction of discontinuities on the junctions between horizontal scan and vortical ui,n. The discontinuities are reduced by using the hmction filtering along the θ direction.
|