Directional interpolation for magnetic resonance angiography

Abstract

The staircase artifact appearing in Magnetic Resonance Angiography boundaries between flowing blood and stationary tissue is eliminated by using a variable local interpolation direction which is determined based on comparing local intensity patterns. This technique of local directional interpolation is applied either to a three dimensional array of voxels prior to projection or to a two dimensional array of pixels after projection. In the case of interpolating lines of further pixels between consecutive lines of original pixels, a window of n.sub.1 pixels in a present line is compared to successive groups of n.sub.1 pixels in a search window of n.sub.2 .gtoreq.n.sub.1 pixels which groups are successively shifted in position in the search window. A match measure is formed by either a correlation or a root mean squared error (or a combination thereof) between the window and groups compared. The best match with respect to a threshold determines corresponding pixels. In the absence of a match better than the threshold a default vertical direction of interpolation is taken.