write_trajectory#

mrinufft.io.nsp.write_trajectory(trajectory: ndarray, FOV: tuple[float, float, float], img_size: tuple[int, int, int], grad_filename: str, norm_factor: float = 0.5, gamma: float = 42576.0, raster_time: float = 0.01, check_constraints: bool = True, TE_pos: float = 0.5, gmax: float = 0.04, smax: float = 0.1, pregrad: str | None = None, postgrad: str | None = None, grad_method: str = 'auto', version: float = 5, **kwargs)[source]#

Calculate gradients from k-space points and write to file.

Parameters:

  • trajectory (np.ndarray) – Trajectory in k-space points. Shape (num_shots, num_samples_per_shot, dimension).

  • FOV (tuple) – Field of view

  • img_size (tuple) – Image size

  • grad_filename (str) – Gradient filename

  • norm_factor (float, optional) – Trajectory normalization factor, by default 0.5

  • gamma (float, optional) – Gyromagnetic ratio in kHz/T, by default 42.576e3

  • raster_time (float, optional) – Gradient raster time in ms, by default 0.01

  • check_constraints (bool, optional) – Check scanner constraints, by default True

  • TE_pos (float, optional) – The ratio of trajectory when TE occurs, with 0 as start of trajectory and 1 as end. By default 0.5, which is the center of the trajectory (in-out trajectory).

  • gmax (float, optional) – Maximum gradient magnitude in T/m, by default 0.04

  • smax (float, optional) – Maximum slew rate in T/m/ms, by default 0.1

  • pregrad (str, optional) – Pregrad method, by default prephase prephase will add a prephasing gradient to the start of the trajectory.

  • postgrad (str, optional) – Postgrad method, by default ‘slowdown_to_edge’ slowdown_to_edge will add a gradient to slow down to the edge of the k-space along x-axis for all the shots i.e. go to (Kmax, 0, 0). This is useful for sequences needing a spoiler at the end of the trajectory. However, spoiler is still not added, it is expected that the sequence handles the spoilers, which can be variable. slowdown_to_center will add a gradient to slow down to the center of the k-space.

  • version (float, optional) – Trajectory versioning, by default 5

  • kwargs (dict, optional) – Additional arguments for writing the gradient file. These are arguments passed to write_gradients function above.