pygrappa.grappaop

Python implementation of the GRAPPA operator formalism.

pygrappa.grappaop.grappaop(calib, coil_axis=-1, lamda=0.01)[source]

GRAPPA operator for Cartesian calibration datasets.

Parameters:
  • calib (array_like) – Calibration region data. Usually a small portion from the center of kspace.
  • coil_axis (int, optional) – Dimension holding coil data.
  • lamda (float, optional) – Tikhonov regularization parameter. Set to 0 for no regularization.
Returns:

Gx, Gy – GRAPPA operators for both the x and y directions.
Return type:

array_like

Notes

Produces the unit operator described in [1].

This seems to only work well when coil sensitivities are very well separated/distinct. If coil sensitivities are similar, operators perform poorly.

References

[1]Griswold, Mark A., et al. “Parallel magnetic resonance imaging using the GRAPPA operator formalism.” Magnetic resonance in medicine 54.6 (2005): 1553-1556.