PMC

Retrospective selection of temporal resolution: (a) Comparison of unaliased FOV between the golden-ratio view order and conventional bit-reversed 13-interleaf UDS sampling. (b) The enlargement of the region within the green rectangle in (a). The blue shaded region in (a,b) indicates that unaliased FOV varies in conventional bit-reversed 13-interleaf UDS when the number of TRs is less than 10. The black solid line illustrates a linear relationship between unaliased FOV and temporal resolution when UDS trajectories are designed under the constraints of the same spatial resolution and readout duration. Note that the unaliased FOV is fixed as 20 cm for a temporal window length (≥13-TR) for the conventional bit-reversed 13-interleaf UDS, but it increases with temporal window length for the golden-ratio view order.

k-space trajectories for (a) conventional bit-reversed 13-interleaf UDS and (b) golden-ratio spiral view order when samples from 13 consecutive TRs are combined. Temporal view orders are marked with the numbers on each end of the spiral interleaves. In (a), the angle spacing between spatially adjacent spiral interleaves is uniform with an angle of 360°/13. In (b), the angle spacing between spatially adjacent spiral interleaves is not uniform but the angle increment in successive view numbers is uniform with an angle of .

Gridding reconstructed dynamic frames and time intensity profiles from (a,c) bit-reversed 13-interleaf uniform density spiral data and (b,d) spiral golden-ratio view order data. A 40 × 40 matrix containing only the vocal tract region of interest is shown. Retrospective selection of temporal resolution is performed using 8-TR and 13-TR in (a), and 8-TR, 13-TR, and 21-TR in (b). Frame update rate was 1-TR = 6.164 ms. Two example frames (frame 1, 6) are shown (frame 1 is relatively stationary and frame 6 is captured during rapid tongue tip motion). Time intensity profiles from the image column indicated by the dashed lines are shown for (c) bit-reversed 13-interleaf UDS and (d) golden-ratio view order data.

A schematic showing angular interleaving for radial LGE. For simplicity in illustration purposes, interleaving is demonstrated for a 2D radial acquisition, although the actual acquisition used a 3D radial acquisition with the end points of spokes distributed across the unit sphere. In this schematic, there are N=8 views acquired after each of the 2 inversion pulses. The 8 views are acquired in a bit-reversed order so that each additional view seeks to evenly divide the unit circle (sphere) into approximately equal pieces. This also will divide the unit circle (sphere) into equal pieces when any subgroup of W (W<=N) consecutive projections are used. Additional interleaving is performed so that projections from identical subgroups acquired after different and consecutive inversion pulses can be combined to further subdivide the unit circle (sphere) into approximately equal pieces.