3D stack-of-spirals spin echo

A slab-selective excitation and 180-degree refocusing pulse form one spin echo, followed by a spiral interleaf with Cartesian partition encoding. Spoilers suppress unwanted coherence between repetitions. TE controls T2 weighting; off-resonance affects the spiral readout. This sequence supports rapid 3D T2-weighted imaging.

Sixteen interleaves

Sixteen interleaves at every partition.

import pypulseqpp as pp
from pypulseqpp.sequences import se_stack_of_spirals3D_sequence

baseline = se_stack_of_spirals3D_sequence(
    n=96, n_z=8, n_shots=16, te=None, tr=None, n_dummy=0
)
print(f"{baseline.num_blocks} blocks, {baseline.duration()[0]:.2f} s")

1024 blocks, 1.90 s

Sequence diagram

baseline.paper_plot()

Sampling order

The interleaves of every partition, over the three k-space axes.

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

Fewer interleaves

Halving the interleaf count doubles the pitch and undersamples the peripheral k-space disc.

alternative = se_stack_of_spirals3D_sequence(
    n=96, n_z=8, n_shots=8, te=None, tr=None, n_dummy=0
)

                   blocks  duration (s)  acquisitions
16 interleaves       1024          1.90           128
8 interleaves         512          1.10            64

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