2D PROPELLER gradient echo

A spoiled low-flip-angle excitation is followed by one Cartesian line from a rotating PROPELLER blade. Gradient and RF spoiling suppress residual transverse coherence between repetitions. TR, flip angle, and TE determine contrast. The overlapping central k-space region supports motion estimation in structural imaging.

Sixteen-line blades

Sixteen lines per blade, with the number of blade orientations chosen to cover the k-space disc.

import pypulseqpp as pp
from pypulseqpp.sequences import gre_propeller2D_sequence

baseline = gre_propeller2D_sequence(
    n=192, blade_width=16, n_slices=1, te=None, tr=None, n_dummy=0
)
print(f"{baseline.num_blocks} blocks, {baseline.duration()[0]:.2f} s")

1824 blocks, 2.67 s

Sequence diagram

baseline.paper_plot()

Sampling order

The colour encodes blade acquisition order. Each blade is a band of parallel lines; the bands overlap at the centre.

pp.plot.plot_kspace(baseline, color_by="shot", plane="xy")

Wider blades

Increasing the blade width reduces the number of blade orientations and increases the duration of each blade. The larger shared central-k-space region provides additional data for motion estimation.

alternative = gre_propeller2D_sequence(
    n=192, blade_width=32, n_slices=1, te=None, tr=None, n_dummy=0
)

                   blocks  duration (s)  acquisitions
16 lines             1824          2.67           304
32 lines             1920          2.81           320

pp.plot.plot_kspace(alternative, color_by="shot", plane="xy")