initialize_3D_wave_caipi#
- mrinufft.trajectories.trajectory3D.initialize_3D_wave_caipi(Nc_or_R: int | tuple[int, int], Ns: int, nb_revolutions: float = 5, width: float = 1, packing: str = 'triangular', shape: str | float = 'square', spacing: tuple[int, int] = (1, 1), readout_axis: int = 0, wavegrad: float | tuple[float, float] | 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.
