2D PROPELLER spin echo

A slice-selective excitation and 180-degree refocusing pulse form one spin echo, at which one line of a rotating PROPELLER blade is acquired. Spoilers suppress unwanted coherence before the next TR. TE controls T2 weighting and TR controls longitudinal recovery. The overlapping blade centres support motion-robust structural imaging.

Sixteen-line blades

Sixteen lines per blade.

import pypulseqpp as pp
from pypulseqpp.sequences import se_propeller2D_sequence

baseline = se_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")

2736 blocks, 5.45 s

Sequence diagram

baseline.paper_plot()

Sampling order

Colour encodes blade acquisition order.

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

Wider blades

Wider blades cover the k-space disc with fewer blade orientations, and each blade samples a larger central region.

alternative = se_propeller2D_sequence(
    n=192, blade_width=32, n_slices=1, te=None, tr=None, n_dummy=0
)

                   blocks  duration (s)  acquisitions
16 lines             2736          5.45           304
32 lines             2880          5.73           320

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