pygrappa.gfactor

Calculate g-factor maps.

pygrappa.gfactor.gfactor(coils, Rx, Ry, coil_axis=-1, tol=1e-06)[source]

Compute g-factor map for coil sensitities and accelerations.

Parameters:
  • C (array_like) – Array of coil sensitivities
  • Ry (int) – x acceleration
  • Ry – y acceleration
  • coil_axis (int, optional) – Dimension holding coil data.
  • tol (float, optional) –
Returns:

g – g-factor map
Return type:

array_like

Notes

Adapted from John Pauly’s MATLAB script found at [1].

References

[1]https://web.stanford.edu/class/ee369c/restricted/ Solutions/assignment_4_solns.pdf
pygrappa.gfactor.gfactor_single_coil_R2(coil, Rx=2, Ry=1)[source]

Specific example of a single homogeneous coil, R=2.

Parameters:
  • coil (array_like) – Single coil sensitivity.
  • Ry (int) – x acceleration
  • Ry – y acceleration
Returns:

g – g-factor map
Return type:

array_like

Notes

Analytical solution for a single, homogeneous coil with an undersampling factor of R=2. Equation 11 in [2].

Comparing head-to-head with pygrappa.gfactor(), this does produce different results. I don’t know which one is more correct…

References

[2]Blaimer, Martin, et al. “Virtual coil concept for improved parallel MRI employing conjugate symmetric signals.” Magnetic Resonance in Medicine: An Official Journal of the International Society for Magnetic Resonance in Medicine 61.1 (2009): 93-102.