SpinEchoSimulator

class torchsim.simulators.SpinEchoSimulator(*args, **kwargs)

Bases: Simulator

A spin echo repeated every TR, optionally behind an inversion.

The refocusing pulse at TE / 2 inverts what has recovered since the excitation, so the longitudinal magnetization the next excitation finds is 1 - 2 exp(-(TR - TE / 2) / T1) + exp(-TR / T1) of equilibrium [1], and the echo decays with T2. An inversion time multiplies this by the recovery from the inversion, 1 - (1 + inv_efficiency) exp(-TI / T1).

References

[1]

Bernstein, M. A., King, K. F., Zhou, X. J., Handbook of MRI Pulse Sequences, Elsevier (2004), sections 14.2 and 14.3. https://doi.org/10.1016/B978-0-12-092861-3.X5000-6

Examples

from torchsim.simulators import SpinEchoSimulator

sequence = SpinEchoSimulator(TE=(10.0, 30.0, 60.0, 100.0), TR=2000.0)
signal = sequence.simulate(T1=1000.0, T2=(50.0, 100.0))
print(signal.shape)

torch.Size([2, 4])

Methods

bind	This simulator with more fixed on it, values or settings alike.
describe	Return the description this protocol plays.
evaluate	Evaluate the closed form, no state machine and no description.
from_description	Return a simulator over a stream someone else assembled.
from_pulseq	Return a simulator over one repetition of a Pulseq sequence.
jacobian	Return the signal and its derivative with respect to diff.
layout	Return the operators of one repetition, in the order they play.
played	Return the protocol as it will be laid out.
repetition_s	Return how long one repetition lasts, given what the layout played.
simulate	Return the recorded signal.

evaluate(properties, **sequence)

Evaluate the closed form, no state machine and no description.