steady_state_dummies

steady_state_dummies#

pypulseqpp.sequences.steady_state_dummies()[source]#

Return the dummy repetitions that bring a spoiled steady state within tolerance.

The count is of repetitions played before acquiring, so that the longitudinal magnetisation is within tolerance of its steady state. From equilibrium, the distance to the steady state shrinks by exp(-repetition_s / t1_s) * cos(flip) each repetition. A flip of 90 degrees or more reaches it after one; at least one is always played.

Parameters:

  • repetition_s (float) – Time between two excitations of the same magnetisation (s).

  • flip_angle_deg (float) – Excitation flip angle (degrees).

  • t1_s (float, default=STEADY_STATE_T1_S) – T1 the steady state is reached for (s).

  • tolerance (float, default=0.01) – Fraction of the distance from equilibrium to the steady state left.

Raises:

ValueError – If a time or the tolerance is not positive, or the tolerance is not below one.

Examples

>>> from pypulseqpp import sequences
>>> sequences.steady_state_dummies(5e-3, 12.0)
182
>>> sequences.steady_state_dummies(0.5, 90.0)
1