pulpy.grad.waveform.spiral_varden

pulpy.grad.waveform.spiral_varden(fov, res, gts, gslew, gamp, densamp, dentrans, nl, rewinder=False)[source]

Variable density spiral designer. Produces trajectory, gradients, and slew rate. Gradient units returned are in g/cm, g/cm/s

Parameters:

  • fov (float) – imaging field of view (cm).

  • res (float) – imaging isotropic resolution (cm).

  • gts (float) – gradient sample time in sec.

  • gslew (float) – max slew rate in g/cm/s.

  • gamp (float) – max gradient amplitude in g/cm.

  • densamp (float) – duration of full density sampling (# of samples).

  • dentrans (float) – duration of transition from higher to lower (should be >= densamp/2).

  • nl (float) – degree of undersampling outer region.

  • rewinder (Boolean) – if True, include rewinder. If false, exclude.

Returns:

(g, k, t, s, dens) tuple containing

  • g - (array): gradient waveform [g/cm]

  • k - (array): exact k-space corresponding to gradient g.

  • time - (array): sampled time

  • s - (array): slew rate [g/cm/s]

  • dens - (array): undersampling factor at each time point.

Return type:

tuple

References

Code and algorithm based on spiralgradlx6 from Doug Noll, U. of Michigan BME