DiffusionSimulator

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

Bases: Simulator

Attenuation by Gaussian diffusion, at a series of b-values.

The signal is M0 exp(-b D) for an isotropic D [1], or M0 exp(-b g^T D g) for a diffusion tensor along unit gradient directions g, which is what giving directions asks for: the six entries of TENSOR are then the properties, and D is not.

References

[1]

Stejskal, E. O., Tanner, J. E., “Spin diffusion measurements: spin echoes in the presence of a time-dependent field gradient”, The Journal of Chemical Physics 42.1 (1965), pp. 288-292. https://doi.org/10.1063/1.1695690

Examples

from torchsim.simulators import DiffusionSimulator

sequence = DiffusionSimulator(b=(0.0, 500.0, 1000.0, 2000.0))
signal = sequence.simulate(D=(0.8, 3.0))
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.