initialize_3D_wave_caipi#

mrinufft.trajectories.inits.wave_caipi.initialize_3D_wave_caipi(Nc_or_R: int | tuple, Ns: int, nb_revolutions: float = 5, width: float = 1, packing: str = 'triangular', shape: str | float = 'square', spacing: tuple = (1, 1), readout_axis: int = 0, wavegrad: float | tuple | None = None, caipi_delta: int = 0, acq: Acquisition | None = None) → ndarray[tuple[int, ...], dtype[_ScalarType_co]][source]#

Initialize 3D trajectories with Wave-CAIPI.

This implementation is based on the work from [Bil+15].

Parameters:

  • Nc_or_R (int or tuple[int, int]) –

    Number of shots Nc or GRAPPA R factors along the two phase-encoding directions. - If an int is provided, it is interpreted as Nc (number of shots). - If a tuple[int, int] is provided, it is interpreted as

    R (GRAPPA factors).

  • Ns (int) – Number of samples per shot

  • nb_revolutions (float, optional) – Number of revolutions, by default 5

  • width (float, optional) – Diameter of the helices normalized such that width=1 densely covers the k-space without overlap for square packing, by default 1.

  • packing (str, optional) – Packing method used to position the helices: “triangular”/”hexagonal”, “square”, “circular” or “random”/”uniform”, by default “triangular”.

  • shape (str | float, optional) – Shape over the 2D \(k_x-k_y\) plane to pack with shots, either defined as str (“circle”, “square”, “diamond”) or as float through p-norms following the conventions of the ord parameter from numpy.linalg.norm, by default “circle”.

  • spacing (tuple[int, int]) – Spacing between helices over the 2D \(k_x-k_y\) plane normalized similarly to width to correspond to helix diameters, by default (1, 1).

  • readout_axis (int, optional) – Axis along which the readout is performed, either 0, 1 or 2.

  • wavegrad (float, optional) – Wave gradient amplitude in T/m, by default None If None, the value of width is used to estimate the wave gradient amplitude. acq must be provided if used.

  • acq (Acquisition, optional) – Acquisition parameters, by default None.

Returns:

3D wave-CAIPI trajectory

Return type:

NDArray

References

[Bil+15]

Bilgic, Berkin, Borjan A. Gagoski, Stephen F. Cauley, Audrey P. Fan, Jonathan R. Polimeni, P. Ellen Grant, Lawrence L. Wald, and Kawin Setsompop. “Wave-CAIPI for highly accelerated 3D imaging.” Magnetic resonance in medicine 73, no. 6 (2015): 2152-2162.