I would like to map DTI image with T1w image, For that which DTI image and T1w image should I download from ADNI? Is it ok, if I download the AXIAL DTI and T1w of the same subject in different session. Thanks
Use the DTI and T1w images from the same session for each subject. Any scan session that had a DTI would have had a T1w, so there should be no need to cross sessions.
You will need to synthesize a T1-like contrast from the full (4D) diffusion image, which I believe requies downloading the DICOM. See http://brainsuite.org/processing/diffusion/pipeline/