espirit#

mrinufft.extras.smaps.espirit(traj: ndarray[tuple[int, ...], dtype[_ScalarType_co]], shape: tuple[int, ...], kspace_data: ndarray[tuple[int, ...], dtype[_ScalarType_co]], backend: str, density: ndarray[tuple[int, ...], dtype[_ScalarType_co]] | None = None, max_iter: int = 10, calib_width: int | tuple[int, ...] = 24, kernel_width: int | tuple[int, ...] = 6, thresh: float = 0.02, crop: float = 0.95, decim: int = 1) → ndarray[tuple[int, ...], dtype[_ScalarType_co]][source]#

ESPIRIT algorithm on non-Cartesian data.

Parameters:

  • traj (numpy.ndarray) – The trajectory of the samples.

  • shape (tuple) – The shape of the image.

  • kspace_data (numpy.ndarray) – The k-space data.

  • threshold (float, or tuple of float, optional) – The threshold used for extracting the k-space center. By default it is 0.1

  • backend (str) – The backend used for the operator.

  • density (numpy.ndarray, optional) – The density compensation weights.

  • max_iter (int, optional) – The max iterations for internal pinv computations

Return type:

ndarray[tuple[int, …], dtype[_ScalarType_co]]

calib_widthint or tuple of int, optional

The calibration region width. By default it is 24.

kernel_widthint or tuple of int, optional

The kernel width. By default it is 6.

threshfloat, optional

The threshold for the singular values. By default it is 0.02.

cropfloat, optional

The cropping threshold for the sensitivity maps. By default it is 0.95.

decimint, optional

The decimation factor for the caluclation of sensitivity maps. By default it is 1. This can be used to speed up the computation and significantly reduce memory usage. The final result is upsampled back to the original size through linear interpolation.

Returns:

Smaps – The sensitivity maps

Return type:

NDArray

Returns:

Smaps – The sensitivity maps.

Return type:

numpy.ndarray

References

Uecker M, Lai P, Murphy MJ, Virtue P, Elad M, Pauly JM, Vasanawala SS, Lustig M. ESPIRiT–an eigenvalue approach to autocalibrating parallel MRI: where SENSE meets GRAPPA. Magn Reson Med. 2014 Mar;71(3):990-1001. doi: 10.1002/mrm.24751. PMID: 23649942; PMCID: PMC4142121.