Arbitrary

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Arbitrary#

class pypulseqpp.sequences.Arbitrary[source]#

Bases: NonCartesianGradient

Base interleaf from a caller-supplied 2D or 3D k-space path.

A path not starting at k = 0 gets prewinders, and one not ending there gets rewinders. The readout is stretched to last at least its sample count over bandwidth_hz_px, and the dwell is the longest on the ADC raster that fits the samples in it.

Parameters:

  • system (Opts) – System limits.

  • trajectory (ArrayLike) – (n, 2) or (n, 3) k-space path (1/m), with n >= 4. Its samples set the geometry; the solver sets the timing.

  • matrix (int) – Matrix size. The ADC takes round(matrix * oversamp) samples, rounded down to system.adc_samples_divisor.

  • bandwidth_hz_px (float, default=250000.0) – Requested 1 / dwell (Hz).

  • oversamp (float, default=1.0) – ADC oversampling, at least one.

  • axes (Sequence[str], default=None) – Channel per path component; the first two or three of x, y, z by default.

  • solver_oversampling (int, default=8) – Path-resampling factor of the time-optimal solver.

  • derate (bool, default=True) – Apply pypulseqpp.apply_system_derates() first.

Raises:

ValueError – If trajectory has the wrong shape, axes does not name one distinct channel per component, or a size is out of range.

Examples

A spoke written as a path starts and ends away from k = 0, so it requires a prewinder and a rewinder:

>>> import numpy as np
>>> import pypulseqpp.sequences as design
>>> import pypulseqpp as pp
>>> kmax = 64 / (2 * 0.22)
>>> spoke = np.column_stack([np.linspace(-kmax, kmax, 64), np.zeros(64)])
>>> path = design.Arbitrary(pp.Opts(), spoke, matrix=64)
>>> path.has_prewinder, path.has_rewinder, path.n_samples
(True, True, 64)

One spoke given as a k-space path, and the waveform the solver traces it with. The prewinder and rewinder are solved separately and are not part of the readout waveform drawn here:

(svg)

../_images/pypulseqpp-sequences-Arbitrary-1.svg

Methods

rotated

Return this interleaf rotated in its own plane, with unchanged timing.

Attributes

axes

The gradient channels this interleaf drives, in waveform order.

gx

Gradient on channel x, or None when this interleaf does not drive it.

gy

Gradient on channel y, or None when this interleaf does not drive it.

gz

Gradient on channel z, or None when this interleaf does not drive it.

has_prewinder

Whether a prewinder leads from k = 0 to the start of the path.

has_rewinder

Whether a rewinder leads from the end of the path back to k = 0.
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