FourierPlayer

class pulserver.virtual.FourierPlayer

Bases: object

The blocks the cache beside a sequence file plays, acquired of a phantom’s tissue by the Fourier engine.

Each pulse turns an entry ideally, through its flip angle on resonance times the magnitude of the transmit field the entry sees and the pulse’s own profile at the field the entry sees during it, about its axis turned by the transmit field’s phase. Between pulses and readouts, the net moment of the gradients across a voxel shifts the configuration states by one order where it dephases by at least SHIFT_CYCLES cycles along the axes the tissue spans; its part that changes from one repetition to the next counts where the intervals between two pulses do not cancel it, and anything less is taken as balanced. Entries a pulse turns alike form a group, and the groups an excitation turns form a station: its readouts, and a stream of the events that act on its groups, a train per group, over each class of tissue, bin of the field and bin of the transmit field the entries interpolate between, simulated by blochsim’s extended phase graphs. At each readout’s echo, the sample nearest the centre of k-space, those signals are spanned by a temporal basis. Across the readout, each entry decays with its T2 from the echo, dephases with its T2’ over the time the magnetization has gone unrefocused, and precesses at its frequency from the echo, spanned by a basis of the samples’ times. A station’s readouts encode one image per pair of terms, sampled on a grid along the logical axes the trajectory encodes, at the resolution its widest k reaches, over the entries it excites, each entry a cube of uniform magnetization. Each image times each coil’s sensitivity is transformed to the samples by bartorch’s NUFFT.

Parameters:

• seq_path – The first file of the sequence’s chain, beside its cache.

• tissue – The phantom’s tissue.

• cache_ext – The extension of the cache beside each file.

• rotation – (3, 3) rotation of the prescription from logical to physical axes; the identity by default.

• device – Where the simulation runs; a card where there is one by default.

• tolerance – The relative residual of the bases.

• motion – How the subject moves, at each readout’s echo; it moves its encoding alone, its excitation, relaxation and coil sensitivities following it.

• girf – The impulse response the gradients play through.

Attributes:

played – The playout’s blocks, as pulserver.ir.playout() records them.

Methods

boundary	Return the first block from block on at which a span of the scan may end.
readouts	Yield each readout of the blocks from first to before last: (coils, samples) complex64, demodulated.

Attributes

blocks

Blocks in the scan.