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Using MRIGradients for spiral pulseq sequence #17

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aTrotier opened this issue Jul 12, 2024 · 0 comments
Open

Using MRIGradients for spiral pulseq sequence #17

aTrotier opened this issue Jul 12, 2024 · 0 comments

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@aTrotier
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aTrotier commented Jul 12, 2024

Hi,
After playing around with the package and finding that most of the issues are due to some conversion problem from raw -> acq (pulseq split the ADC in 28):

for p in eachindex(raw.profiles)
  raw.profiles[p].traj = Float32.(traj[:,:,p])
  raw.profiles[p].head.trajectory_dimensions=2
  # issue with reverse
  raw.profiles[p].head.read_dir = (0.0,0.0,0.0)
end
raw.params["trajectory"] = "custom"
raw.params["encodedSize"] = (64,64)
raw.params["fov"] = (256,256,3)

# convert to acq
acq = AcquisitionData(raw)
acq.fov = (256,256,3)
acq.traj[1].circular = false #Removing circular window
acq.traj[1].numSamplingPerProfile = size(acq.kdata[1],1) #correct the issue with 28
acq.traj[1].numProfiles = 1 #correct the issue with 28
acq.traj[1].times = 0:raw.profiles[1].head.sample_time_us:raw.profiles[1].head.sample_time_us*(size(acq.kdata[1],1)-1)

The results seems okish except for the first points :
Screenshot 2024-07-11 at 16 41 30

Do you also observe the fluctuation at the start in your experiments ?

By the way, I am not really familiar with spiral imaging and images are pretty bad :
Phantom with the spiral pulseq example https://pulseq.github.io/writeSpiral.html :
image

Brain with my own spiral implementation where dt is small (10us like the gradient raster time and I have a few starting points equal to 0 for Self-gating (should I remove the SG points from trajectory before applying girf ?):
image

image

Maybe gradient intensity is too high and I have a FOV/2, or it is only an issue with the B0 / spatial resolution...
Any thoughts ?

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