deepmr.sinusoidal_fa#
- deepmr.sinusoidal_fa(fa_max=(35.0, 43.0, 70.0, 45.0, 27.0), length=200, spacing=10, recovery=0, offset=5.0, head=None)[source]#
Design a multi-segment sinusoidal flip angle train.
The resulting train, similar to the one introduced by Jiang et al. [1], consists of
len(fa_max)
sinusoidal section (positive wave), each of lengthlength` separed by constant flip angle sections of length ``spacing
. Then
-th sinusoidal section peaks atfa_max[n] [deg]
. The train is followed by a constant flip angle section of lengthrecovery
. The overall schedule minimum flip angle is determined by theoffset
parameter (in[deg]
).- Parameters:
fa_max (Iterable[float], optional) – Maximum flip angle in
[deg]
per sinusoidal segment. The default is(35., 43., 70., 45., 27.) [deg]
.length (int, optional) – Sinusoidal segment length. The default is
200
pulses.spacing (int, optional) – Zero degrees flip angle pulses in between segments. The default is
10
.recovery (int, optional) – Constant flip angle recovery train length. The default is
0
.offset (float, optional) – Minimum flip angle in
[deg]
. The default is5. [deg]
.head (Header, optional) – Pre-existing acquisition header. If provided, interpolate FA train to
ncontrast = head.traj.shape[0]
and include it in thehead.FA
field. The default isNone
.
- Returns:
If
head
is not provided, returns sinusoidal flip angle train in[deg]
as atorch.Tensor
. Ifhead
is provided, insert flip angle train (linearly interpolated toncontrast = head.traj.shape[0]
) inhead.FA
field.- Return type:
torch.Tensor | deepmr.Header
Examples
>>> import deepmr
A
5
sections flip angle train with10
-pulses long separation and no recovery (e.g., for 2D MR Fingerprinting) can be generated as:>>> fa_train = deepmr.sinusoidal_fa((35., 43., 70., 45., 27.), 200, 10)
A final
100
constant flip angle segment (e.g., for 3D MR Fingerprinting) can be added via therecovery
argument:>>> fa_train = deepmr.sinusoidal_fa((35., 43., 70., 45., 27.), 200, 10, recovery=100)
References
[1] Jiang, Y., Ma, D., Seiberlich, N., Gulani, V. and Griswold, M.A. (2015), MR fingerprinting using fast imaging with steady state precession (FISP) with spiral readout. Magn. Reson. Med., 74: 1621-1631. https://doi.org/10.1002/mrm.25559