(a,b) A fully-sampled HARDI dataset is used to illustrate the proposed sampling and ordering scheme in ky – d space. The present implementation sampled one out of every four ky lines, as shown in the lower row in (b), and employed a smooth ordering along d, as shown in the middle column in (b). (c) The undersampled data were then reconstructed using the proposed algorithm, depicted here with a block diagram. See text for more details.