snake.core.sampling.samplers

Samplers generate kspace trajectories.

Module Contents

Classes

NonCartesianAcquisitionSampler	Base class for non-cartesian acquisition samplers.
LoadTrajectorySampler	Load a trajectory from a file.
StackOfSpiralSampler	Spiral 2D Acquisition Handler to generate k-space data.
RotatedStackOfSpiralSampler	Spiral 2D Acquisition Handler to generate k-space data.
EPI3dAcquisitionSampler	Sampling pattern for EPI-3D.
EVI3dAcquisitionSampler	SAmpler for EVI acquisition.

Functions

dir_cos

Compute the directional cosine of the vector from beg to end point.

API

class snake.core.sampling.samplers.NonCartesianAcquisitionSampler

Bases: snake.core.sampling.base.BaseSampler

Base class for non-cartesian acquisition samplers.

Parameters:

• constant (bool) – If True, the trajectory is constant.

• obs_time_ms (int) – Time spent to acquire a single shot

• in_out (bool) – If true, the trajectory is acquired with a double join pattern from/to the periphery

• ndim (int) – Number of dimensions of the trajectory (2 or 3)

__engine__ = 'NUFFT'

in_out: bool = True

obs_time_ms: int = 30

add_all_acq_mrd(dataset: ismrmrd.Dataset, sim_conf: snake.core.simulation.SimConfig) → ismrmrd.Dataset

Generate all mrd_acquisitions.

class snake.core.sampling.samplers.LoadTrajectorySampler

Bases: snake.core.sampling.samplers.NonCartesianAcquisitionSampler

Load a trajectory from a file.

Parameters:

• constant (bool) – If True, the trajectory is constant.

• obs_time_ms (int) – Time spent to acquire a single shot

• in_out (bool) – If true, the trajectory is acquired with a double join pattern from/to the periphery

__sampler_name__ = 'load-trajectory'

__engine__ = 'NUFFT'

path: str = None

constant: bool = True

obs_time_ms: int = 25

raster_time: float = 0.05

in_out: bool = True

_single_frame(sim_conf: snake.core.simulation.SimConfig) → numpy.typing.NDArray

Load the trajectory.

class snake.core.sampling.samplers.StackOfSpiralSampler

Bases: snake.core.sampling.samplers.NonCartesianAcquisitionSampler

Spiral 2D Acquisition Handler to generate k-space data.

Parameters:

• acsz (float | int) – Number/ proportion of lines to be acquired in the center of k-space.

• accelz (int) – Acceleration factor for the rest of the lines.

• directionz (Literal["center-out", "random"]) – Direction of the acquisition. Either “center-out” or “random”.

• pdfz (Literal["gaussian", "uniform"]) – Probability density function of the sampling. Either “gaussian” or “uniform”.

• obs_ms (int) – Time spent to acquire a single shot

• nb_revolutions (int) – Number of revolutions of the spiral.

• in_out (bool) – If true, the spiral is acquired with a double join pattern from/to the periphery

• **kwargs – Extra arguments (smaps, n_jobs, backend etc…)

__sampler_name__ = 'stack-of-spiral'

acsz: float | int = None

accelz: int = None

orderz: str | snake.core.sampling.factories.VDSorder = None

nb_revolutions: int = 10

spiral_name: str = 'archimedes'

pdfz: str | snake.core.sampling.factories.VDSpdf = None

constant: bool = False

in_out: bool = True

rotate_angle: snake.core.sampling.factories.AngleRotation = None

obs_time_ms: int = 30

n_shot_slices: int = 1

_single_frame(sim_conf: snake.core.simulation.SimConfig) → numpy.typing.NDArray

Generate the sampling pattern.

class snake.core.sampling.samplers.RotatedStackOfSpiralSampler

Bases: snake.core.sampling.samplers.StackOfSpiralSampler

Spiral 2D Acquisition Handler to generate k-space data.

Parameters:

• rotate_frame_angle (AngleRotation | int) – Angle of rotation of the frame.

• frame_index (int) – Index of the frame.

• **kwargs – Extra arguments (smaps, n_jobs, backend etc…)

__sampler_name__ = 'rotated-stack-of-spiral'

rotate_frame_angle: snake.core.sampling.factories.AngleRotation | int = 0

frame_index: int = 0

fix_angle_rotation(frame: collections.abc.Generator[numpy.ndarray, None, None], angle: snake.core.sampling.factories.AngleRotation | float = 0) → collections.abc.Generator[numpy.ndarray, None, None]

Rotate the trajectory by a given angle.

get_next_frame(sim_conf: snake.core.simulation.SimConfig) → numpy.typing.NDArray

Generate the next rotated frame.

class snake.core.sampling.samplers.EPI3dAcquisitionSampler

Bases: snake.core.sampling.base.BaseSampler

Sampling pattern for EPI-3D.

__sampler_name__ = 'epi-3d'

__engine__ = 'EPI'

in_out = True

acsz: float | int = None

accelz: int = None

orderz: snake.core.sampling.factories.VDSorder = None

pdfz: snake.core.sampling.factories.VDSpdf = None

_single_frame(sim_conf: snake.core.simulation.SimConfig) → numpy.typing.NDArray

Generate the sampling pattern.

add_all_acq_mrd(dataset: ismrmrd.Dataset, sim_conf: snake.core.simulation.SimConfig) → ismrmrd.Dataset

Create the acquisitions associated with this sampler.

class snake.core.sampling.samplers.EVI3dAcquisitionSampler

Bases: snake.core.sampling.base.BaseSampler

SAmpler for EVI acquisition.

__sampler_name__ = 'evi'

__engine__ = 'EVI'

in_out = True

_single_frame(sim_conf: snake.core.simulation.SimConfig) → numpy.typing.NDArray

Generate the sampling pattern.

add_all_acq_mrd(dataset: ismrmrd.Dataset, sim_conf: snake.core.simulation.SimConfig) → ismrmrd.Dataset

Create the acquisitions associated with this sampler.

snake.core.sampling.samplers.dir_cos(start: numpy.typing.NDArray, end: numpy.typing.NDArray) → tuple[numpy.float32]

Compute the directional cosine of the vector from beg to end point.