Fig. 3

K-space efficiencies. Three k-space acquisition modifications demonstrated for a 3D Cartesian sequence. Representations of partial Fourier in the phase-encoding (a) and readout (partial-echo) (b) directions are shown, with dashed lines denoting data points that are not acquired but later calculated (see text). Zero padding (c) has lines of ‘data’ filled with zeros added either side of the acquired data before reconstruction, artificially increasing resolution. An elliptical shutter (d) does not acquire the corner regions of k-space, as they are deemed less critical. Each of these methods can be applied in any encoding direction and those chosen here are simply illustrative