"""Common preparation blocks."""
__all__ = ["InversionPrep", "T2Prep"]
from .. import ops
[docs]def InversionPrep(TI, T1, T2, weight, k, inv_props):
"""
Adiabatic inversion operator.
Consists of a 180° pulse followed by a crusher gradient.
Parameters
----------
TI : torch.Tensor
Inversion time in ``[ms]``.
T1 : torch.Tensor
T1 relaxation time of shape ``(..., npools) in ``[ms]``.
T2 : torch.Tensor
T2 relaxation time of shape ``(..., npools) in ``[ms]``.
weight : torch.Tensor
Pool relative fraction.
k : torch.Tensor
Chemical exchange matrix ``(...., npools, npools)`` in ``[Hz]``.
prep_props : dict
Extra pulse parameters.
Returns
-------
PrepPulse : deepmr.bloch.Operator
Adiabatic Inversion pulse operator, including crusher.
"""
if TI is not None and TI != 0.0:
# parse inversion properties
if inv_props is None:
inv_props = {}
# prep operator
Tinv = ops.AdiabaticPulse(
T1.device, alpha=180.0, name="Inversion Pulse", **inv_props
)
Einv = ops.Relaxation(
T1.device, TI, T1, T2, weight, k, name="Preparation Interval"
)
Sinv = ops.Spoil(name="Inversion Crusher")
return ops.CompositeOperator(Sinv, Einv, Tinv, name="Inversion Propagator")
else:
return ops.Identity(name="Inversion Propagator")
[docs]def T2Prep(Tprep, T1, T2, weight, k, prep_props):
"""
T2 prep operator.
Consists of a 90°-180°--90° composite pulse followed by a crusher gradient.
Parameters
----------
Tprep : torch.Tensor
T2 preparation time in ``[ms]``.
T1 : torch.Tensor
T1 relaxation time of shape ``(..., npools) in ``[ms]``.
T2 : torch.Tensor
T2 relaxation time of shape ``(..., npools) in ``[ms]``.
weight : torch.Tensor
Pool relative fraction.
k : torch.Tensor
Chemical exchange matrix ``(...., npools, npools)`` in ``[Hz]``.
prep_props : dict
Extra pulse parameters.
Returns
-------
PrepPulse : deepmr.bloch.Operator
Adiabatic T2prep pulse operator, including crusher.
"""
if Tprep is not None and Tprep != 0.0:
# parse inversion properties
if prep_props is None:
prep_props = {}
# prep operator
T90p = ops.AdiabaticPulse(
T1.device, alpha=90.0, phi=0.0, name="Flip Pulse", **prep_props
)
Eprep = ops.Relaxation(
T1.device, 0.5 * Tprep, T1, T2, weight, k, name="Preparation Interval"
)
T180 = ops.AdiabaticPulse(
T1.device, alpha=180.0, name="Inversion Pulse", **prep_props
)
T90m = ops.AdiabaticPulse(
T1.device, alpha=90.0, phi=-180.0, name="Flip-back Pulse", **prep_props
)
Sprep = ops.Spoil(name="Prep Crusher")
return ops.CompositeOperator(
Sprep, T90m, Eprep, T180, Eprep, T90p, name="T2prep Propagator"
)
else:
return ops.Identity(name="T2prep Propagator")
