Fig. 2
Streams of sorted pseudo-projections for motion tracking and effect of sorting-segment size. a The golden-step (GS) PEs are sorted by ky into segments (size of 8 shown) before execution. The sorting does not affect the original GS motion tracking technique, which follows: Cartesian readouts falling within a near-zero ky zone (known as the “navigator zone”) are considered “pseudo-projections.” To reveal motion, the pseudo-projections’ ky-dependent magnitude variation is corrected, and any remaining variation in time is smoothed. Cardiac motion and respiratory motion are extracted to guide the two-stage data selection, after which cine frames were reconstructed through simple inverse Fourier transform. b The effects of segment size and navigator zone width on pseudo-projections: sorted GS with various segment size are compared to the original GS at typical navigator zone widths. Both cardiac and respiratory cycles are visible at all practical segment sizes, but generally more clearly at lower navigator zone widths. Note that the streams shown here were processed to prioritize cardiac motion; respiratory motion could also be highlighted using the same data (see Figure 3). ROs: readouts