Sequence modules

Reusable block layouts with their timing and gradient waveforms solved, and the non-Cartesian base interleaves the readout modules play. Every module takes the system limits, a pypulseqpp.Opts, as its first argument; flip angles are in degrees, times in s, lengths in m and frequencies in Hz. The published encoding events are templates the scan loop scales before adding the blocks, as Sequence modules describes.

Base classes

Object	Input	Publishes	Purpose
SequenceModule	Arguments forwarded to init_module	blocks, named events on events, center (s)	Base class of reusable block layouts.
RfModule	Arguments forwarded to init_module	As SequenceModule, plus sim_rf of its RF event	Base class of every excitation and preparation module.

Excitation and refocusing

Object	Input	Publishes	Purpose
NonSelectiveExcitation	Flip angle, duration, frequency and phase offsets	rf	Rectangular non-selective excitation.
NonSelectiveRefocusing	Flip angle, duration, crusher cycles and axis	rf_ref, crusher gz_spoil	Rectangular refocusing between two identical crushers.
SpatialSelectiveExcitation	Flip angle, thickness, duration, time-bandwidth product	rf, gz, gz_reph, selection_amplitude (Hz/m)	SLR slice or slab excitation.
SpatialSelectiveRefocusing	Thickness, flip angle, duration, crusher cycles	rf_ref, crusher–plateau–crusher gz, selection_amplitude (Hz/m)	SLR refocusing with crushers joined to the plateau.
SpatialSelective2DExcitation	Flip angle, excitation FOV and matrix, disc or target	rf, one spiral gradient per axis	Small-tip spiral excitation selective in two dimensions.
FrequencySelectiveExcitation	Flip angle, bandwidth, offset (ppm and Hz)	rf, duration_s	SLR excitation of a spectral band.
SpspExcitation	Flip angle, thickness, spectral bandwidth, subpulse count	rf, alternating gz, gz_reph	Spectral-spatial excitation.
SmsExcitation	Flip angle, thickness, slice gap, band count	rf, gz, gz_reph, band offsets (Hz) and positions (m)	Simultaneous multi-slice SLR excitation.
MultibandExcitation	Flip angle, duration, sideband offset, band count	rf, band offsets (Hz), band power fractions	Non-selective excitation with off-resonance sidebands.

Magnetisation preparation

Object	Input	Publishes	Purpose
InversionPreparation	Duration, adiabatic pulse type, bandwidth, crusher cycles	rf_prep, gz_spoil, prep_labels	Non-selective adiabatic inversion.
BlochSiegertPreparation	Frequency offset, duration, peak B1 (Hz)	rf_prep, spoilers, kbs (rad/Hz²)	Off-resonance Fermi pulse for Bloch-Siegert B1 mapping.
DiffusionPreparation	b-value (s/mm²), gradient duration and separation	rf_prep, rf_ref, rf_store, g_diff, spoilers	Non-selective diffusion preparation.
FatSaturation	Offset (ppm), flip angle, bandwidth, optional thickness	rf_prep, spoilers, gz when selective	SLR fat saturation.
IhMtPreparation	Flip angle, frequency offset, duration, pulse count	rf_prep, spoilers, band_offsets_hz	Dual-offset saturation for ihMT.
MtPreparation	Flip angle, frequency offset, duration, pulse count	rf_prep, spoilers	Off-resonance SLR saturation for MT.
OffResonanceSaturation	RF event, pulse count, spoiler cycles	rf_prep, spoilers	Repeated off-resonance saturation pulse.
T1T2Preparation	Preparation echo time, refocusing count	rf_prep, rf_ref, rf_store, spoilers	T2 preparation stored on −z.
T2Preparation	Preparation echo time, final tip, refocusing count	rf_prep, rf_ref, rf_store, spoilers	Adiabatic T2 preparation.

Cartesian readouts

Each readout takes the excitation RF event with its selection gradient events, and a field of view and matrix per encoded axis, readout first; a fast spin-echo readout also takes the refocusing events.

Object	Input	Publishes	Purpose
LineReadout2D	Excitation, FOV, matrix, TE, TR, bandwidth	adc, gx, gx_pre, gy_pre, rewinders, spoiler	Cartesian line, phase-encoded along y.
LineReadout3D	Excitation, FOV, matrix, TE, TR, bandwidth	adc, gx, gx_pre, gy_pre, gz_pre, rewinders	Cartesian line of a 3D slab.
EpiReadout2D	Excitation, FOV, matrix, ETL, scheme, acceleration	adc, gx lobes, gy_blips, prephasers, echo_times (s)	Single- or multi-shot EPI train.
EpiReadout3D	Excitation, FOV, matrix, ETL, scheme, acceleration	adc, gx lobes, gy_blips, gz_blips, prephasers	Slab-selective EPI train, partition-encoded along z.
FseReadout2D	Excitation, refocusing, FOV, matrix, ETL, ESP	rf_ref, adc, gx, phase encodes, echo_times (s)	Slice-selective CPMG echo train.
FseReadout3D	Excitation, refocusing, FOV, matrix, ETL, ESP	rf_ref, adc, gx, gy_pre, gz_pre, echo_times (s)	Single-slab CPMG echo train.
BssfpReadout2D	Excitation, FOV, matrix, TR, half-flip preparation	adc, gx, balanced phase encodes and rewinders	Slice-selective balanced SSFP.
BssfpReadout3D	Excitation, FOV, matrix, TR, half-flip preparation	adc, gx, phase and partition encodes, rewinders	Slab-selective balanced SSFP.
PropellerReadout2D	Excitation, FOV, matrix, blade width, blade count	EPI train events, blade_angles (rad)	2D PROPELLER blade set.
PropellerStackReadout	As PropellerReadout2D, plus fov_z, matrix_z	EPI train events, blade_angles (rad), partition encodes	Stack of 2D PROPELLER blade sets.

Non-Cartesian readouts

NonCartesianReadout takes a solved two-channel interleaf from Non-Cartesian interleaves; the spiral and rosette readouts design theirs from the prescription.

Object	Input	Publishes	Purpose
NonCartesianReadout	Excitation, a NonCartesianGradient, TE, TR	adc, gx, gy, prewinders, rewinders, gz_spoil	Readout of a solved interleaf with its TR budget.
RadialReadout2D	Excitation, FOV, matrix, TE, TR, bandwidth	adc, gx, gy, gz_spoil	Full radial spoke through the centre of a plane.
RadialStackReadout	As RadialReadout2D, plus fov_z, matrix_z	adc, gx, gy, gz_pre, gz_rew	Radial spokes with Cartesian partitions (stack of stars).
RadialProjectionReadout	Excitation, FOV, matrix, TE, TR, bandwidth	adc, gx, gy, gz_spoil	Radial spokes of a 3D projection acquisition.
SpiralReadout2D	Excitation, FOV, matrix, design interleaves, density	adc, gx, gy, prewinders, rewinders, trajectory	One spiral arm in a plane.
SpiralStackReadout	As SpiralReadout2D, plus fov_z, matrix_z	As SpiralReadout2D, plus gz_pre, gz_rew	Spiral arms with Cartesian partitions along z.
SpiralProjectionReadout	As SpiralReadout2D	As SpiralReadout2D	Spiral arms rotated over a sphere.
SpiralNavigator	FOV, matrix, slab thickness, flip angle, navigator TR	excitation, readout, per-plane rotations	Three orthogonal thick-slab spiral navigators.
RosetteReadout2D	Excitation, FOV, matrix, petals, frequency ratio	adc, gx, gy, trajectory	One multi-petal rosette interleaf in a plane.
RosetteStackReadout	As RosetteReadout2D, plus fov_z, matrix_z	As RosetteReadout2D, plus gz_pre, gz_rew	Rosette petals with Cartesian partitions along z.
RosetteProjectionReadout	As RosetteReadout2D	As RosetteReadout2D	Rosette petals rotated over a sphere.
ZteReadout	Non-selective rf, FOV, matrix, spoke directions or count	g_ramp, g_hold, g_read, adc, shot_rotations	Continuous-gradient ZTE shell with its initial and final ramps.

Non-Cartesian interleaves

Each object holds one base interleaf: its readout gradients, its adc, and the prewinders and rewinders to and from k = 0 at zero gradient amplitude. trajectory is in 1/m. The scan loop rotates the interleaf per shot; rotated returns a copy rotated in its plane.

Object	Input	Publishes	Purpose
NonCartesianGradient	Designed gradient events, ADC event, k-space path	The interleaf, as given	Base interleaf from events designed elsewhere.
Arbitrary	k-space path (n, 2) or (n, 3) (1/m), matrix	Solved interleaf, with prewinders and rewinders as needed	Base interleaf from a caller-supplied path.
Spiral	FOV, matrix, design interleaves, direction, density	Solved spiral interleaf	Constant-, variable- or dual-density spiral.
Rosette	FOV, matrix, petals, frequency ratio, echo spacing	Solved interleaf from and to k = 0	Multi-petal rosette.