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== Sequence-parameter considerations ==
== Sequence-parameter considerations ==
* Shimming
* Shimming
** Shimbox: inside brain? Is bottomline shimbox wrt OFC / air transition most important?
** Shimbox: inside brain? Is bottomline shimbox wrt OFC/air transition most important?
** What is a good shim?LINEWIDTH checken voor scannen? Log values
** What is a good shim? Check LINEWIDTH before start EPI? Log values
** Acquire extra B0-scan as check to avoid large B0-gradient?
** 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
** Use Maarten's patch for image based shimming: this patch applies shim to B0-prescan
* TR:  
* TR:  
** for physiological noise correction, aim for 750ms  
** for physiological noise correction, aim for 750ms or less
** minimal TR: to be adjusted on-scanner (not realistic in VM)
** 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)
* 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
* Water Fat Shift: minimal. Increase to reduce TR
* TE hoeft niet in phase: niet belangrijk voor vet want signaal is al dispersed met deze TE. TE~32.23, 27 is te kort.
* TE not phase: not important as fat signal is already dispersed at this TE. TE30-32, 27 to short.
* Geen slice gap (maar waarom?)
* Slice gap optional for voxel sizes <3mm, set to sefault (10%)  
* Acquired/Reconstructed Matrix size should match
* Acquired/Reconstructed Matrix size should match
* Multiband factor * SENSE ~= 6
* Multiband factor * SENSE ~= 6
* Half scan: no. Unless minimal TR deviates more than 10% from shortest. But: see Gradient mode
* Half scan: no. Unless minimal TR deviates more than 10% from shortest. But: see Gradient mode
* Dynamic Stabilization: regular (niet enhanced, kost teveel tijd. Kan ook verstoring geven?)
* Dynamic Stabilization: regular (enhanced optional for longer runs, ~100ms penalty. May give distortion)
* Offc/Ang: free rotatable Yes
* Offc/Ang: free rotatable Yes
* PNS moderate or low
* PNS moderate or low
* Flip angle --> [http://www.mritoolbox.com/ErnstAngle.html Ernst angle] A typical T1 value for gray matter @ 3T: 1330 ms (Kruger, et al, 2001).
* Flip angle --> [http://www.mritoolbox.com/ErnstAngle.html Ernst angle] A typical T1 value for gray matter @ 3T: 1330 ms (Kruger, et al, 2001).
* Planning: stevig anguleren. Read-out richting omdraaien AP-->PA?
* Planning: angulate in parallel to OFC. Change read-out direction? (AP-->PA?
* Equidistant dynamic sampling
* Equidistant dynamic sampling


== distortion correction ==
== distortion correction ==
Create two SE-EPIs for distortion correction (better unwarping in regions with dropout)  
* 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)  


== Data-export ==
== Data-export ==

Revision as of 08:48, 24 January 2018

Multiband

Overview sequences

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

  • 3mm, TR=600ms, MB4 S1.8, FOV 240x240x132mm, WFS12pix (36mm), PNS moderate. Max dyns/time ???
  • 2.5mm, TR=800ms, MB4 S1.8, FOV 240x240x140mm, WFS 14pix (35mm), PNS moderate. Max time ???
  • 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.

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

  • 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)

Data-export

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