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== Overview sequences ==
== Overview sequences ==
All h 10% gap, fat suppression SPIR offset 175Hz
All h 10% gap, fat suppression SPIR offset 175Hz
* 3mm, TR=600ms, MB4 S1.8, FOV 240x240x132mm, WFS12pix (36mm), PNS moderate. Max dyns/time ???
* 3.0mm, TR=0550ms, MB4 S1.5, FOV 240x240x118mm,   WFS 14.2pix (42.6mm), PNS moderate. Max dyns 1820
* 2.5mm, TR=800ms, MB4 S1.8, FOV 240x240x140mm, WFS 14pix (35mm), PNS moderate. Max time ???
* 2.7mm, TR=0700ms, MB4 S1.5, FOV 240x240x140mm, WFS 14 pix (35mm), PNS moderate. Gradient Mode Maximum, Dyn stabilization Regular, Max dyns
* 2mm, TR=1400ms, MB3 S2, FOV=224x224x125, (min TR=1337ms), WFS 21 pix (42mm), PNS low, Gradient Mode Maximum, Dyn stabilization Regular. Max ~1100 dyns, 26 min.  
* 2.0mm, TR=1600ms, MB4 S1.5, FOV=224x224x125mm, WFS 21 pix (42mm), PNS moderate, Gradient Mode Maximum, Dyn stabilization Regular, Max dyns,   26 min.  


== Sequence-parameter considerations ==
== Sequence-parameter considerations ==

Revision as of 12:47, 22 February 2018

Multiband

Overview sequences

All h 10% gap, fat suppression SPIR offset 175Hz

  • 3.0mm, TR=0550ms, MB4 S1.5, FOV 240x240x118mm, WFS 14.2pix (42.6mm), PNS moderate. Max dyns 1820
  • 2.7mm, TR=0700ms, MB4 S1.5, FOV 240x240x140mm, WFS 14 pix (35mm), PNS moderate. Gradient Mode Maximum, Dyn stabilization Regular, Max dyns
  • 2.0mm, TR=1600ms, MB4 S1.5, FOV=224x224x125mm, WFS 21 pix (42mm), PNS moderate, Gradient Mode Maximum, Dyn stabilization Regular, Max dyns, 26 min.

Sequence-parameter considerations

  • Shimming
    • Shimbox: inside brain? Is bottomline shimbox wrt OFC/air transition most important?
    • What is a good shim? Check LINEWIDTH before start EPI? Log values
    • Acquire extra B0-scan as check to avoid large B0-gradient?
    • Use Maarten's patch for image based shimming: this patch applies shim to B0-prescan
  • TR:
    • for physiological noise correction, aim for 750ms or less
    • minimal TR: to be adjusted on-scanner (not realistic in VM)
  • Gradient mode: Set to Enhanced if duty cycle is limiting factor (enormous difference on AMC-wide bore scanner)
  • Water Fat Shift: minimal. Increase to reduce TR
  • TE not phase: not important as fat signal is already dispersed at this TE. TE30-32, 27 to short.
  • Slice gap optional for voxel sizes <3mm, set to sefault (10%)
  • Acquired/Reconstructed Matrix size should match
  • Multiband factor * SENSE ~= 6
  • Half scan: no. Unless minimal TR deviates more than 10% from shortest. But: see Gradient mode
  • Dynamic Stabilization: regular (enhanced optional for longer runs, ~100ms penalty. May give distortion)
  • Offc/Ang: free rotatable Yes
  • PNS moderate or low
  • Flip angle --> Ernst angle A typical T1 value for gray matter @ 3T: 1330 ms (Kruger, et al, 2001).
  • Planning: angulate in parallel to OFC. Change read-out direction? (AP-->PA?)
  • Equidistant dynamic sampling

distortion correction and registration

  • Create second GE-EPI with opposite fatshift direction, set preparation to auto (so it won't perform a second B0 shim) and group the sequences
  • Alternatively create two SE-EPIs for distortion correction (better unwarping around regions with dropout)
  • Perhaps not include dummies and use one of the pre-saturation scans for registration as it has better grey/white matter contrast (see Multiband data registration)

Data-export

  • enhanced dicom does not work for >16k images
  • export nifti
  • export PAR/REC or XML/REC to store sequence parameters