Question Posted 01/25/18:
I just downloaded the first batch of multishell DTI images from ADNI 3. Are the bvals and bvecs for individual DWI stacks contained within the metadata of the .nii files?

Thank you for your time and help.
Response posted 01/26/18 by ADNI MRI Core:
Thank you for your question to the ADNI MRI Core.

Unfortunately, no, but you can easily get the bvals and bvecs by downloading the DICOM files and converting them to .niis yourself. I think the NiFTI download feature is using a generic DICOM-to-NiFTI conversion at LONI, and it is not set up to deliver the diffusion gradient info.

What you should do is:
* Back up a bit and download the DICOM files using the “As Archived” button.
* Use a program such as dcm2niix to convert the DICOM to NiFTI and extract the diffusion gradient info. dcm2niix will write a (4D) .nii, a .bval, and a .bvec, and the latter two are simple ASCII files, usable by most diffusion processing suites.