gs_field_map

Use the geometric solution to the elliptical signal model for field map.

mr_utils.recon.field_map.gs_field_map.gs_field_map(I0, I1, I2, I3, TR, gs_recon_opts=None)[source]

Use the elliptical signal model to estimate the field map.

Parameters:
  • I0 (array_like) – First of the first phase-cycle pair (0 degrees).
  • I2 (array_like) – Second of the first phase-cycle pair (180 degrees).
  • I1 (array_like) – First of the second phase-cycle pair (90 degrees).
  • I3 (array_like) – Second of the second phase-cycle pair (270 degrees).
  • TR (float) – Repetition time of acquisitons in ms.
  • gs_recon_opts (dict, optional) – Options to pass to gs_recon.
Returns:

gsfm – Wrapped field map in hertz.
Return type:

array_like

Notes

I0, I2 and I1, I3 must be phase-cycle pairs, meaning I0, I2 are separated by 180 degrees and I1, I3 are separated by 180 degrees. It does not matter what the actual phase-cycles are.

Implements field map estimation given in [1].

References

[1]Taylor, Meredith, et al. “MRI Field Mapping using bSSFP Elliptical Signal model.” Proceedings of the ISMRM Annual Conference (2017).