1. Yes
2. Yes
3. Use the preprocessed data which has all files preprocessed and combined
appropriately in ${StudyFolder}/${Subject}/T1w/Diffusion. If you are using
your own diffusion model, be sure to take into account the gradient
nonlinearity effects on the diffusion weighting and direction described in the
grad_dev file. There is some matlab code somewhere that describes this.
4. Also use the preprocessed data as above.
Peace,
Matt.
From:
<hcp-users-boun...@humanconnectome.org<mailto:hcp-users-boun...@humanconnectome.org>>
on behalf of Shruti Narasimham <naras...@tcd.ie<mailto:naras...@tcd.ie>>
Date: Wednesday, July 26, 2017 at 9:49 AM
To: "hcp-users@humanconnectome.org<mailto:hcp-users@humanconnectome.org>"
<hcp-users@humanconnectome.org<mailto:hcp-users@humanconnectome.org>>
Subject: [HCP-Users] Clarification regarding DWI datasets
Dear all,
I am new to the HCP datasets and therefore a bit confused about the DWI
datasets uploaded. I would be very grateful if you could kindly clarify the
following:
1. 3T DWI data has scans with b-values 0,1000,2000,3000 while 7T has with
0,1000,2000 ?
2. Each subject has multi-shell data (different b-values within the same
dataset) ?
3. The manual says that for the 3T data, 6 files exist for each subject
corresponding to 3 b-values and 2 phase encoding directions. The 3T data has
subject_name_dir95_AP, subject_name_dir96_AP, subject_name_dir97_AP,
subject_name_dir95_PA, and so on. I understand that AP , PA corresponds to the
phase encoding direction but what are the different files for (dir 95, 96, 97)
if according to point 2., each file has different b-values? Why do 6 files
exist in each subject's folder? If these are for different gradient tables
used, for CSD tractography can I choose any one file with its corresponding
bval and bvec file for analyses?
4. Same goes for the 7T data, what do the dir71 and dir72 mean? How do these
files differ? I couldn't find any information for the 7T data in the manual.
Apologies for the very basic questions.
Looking for any help / clarification regarding these.
Thank you.
Regards,
Shruti
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