Users familiar with command line can automate downloads and some analysis of data on XNAT via PyXNAT: https://pythonhosted.org/pyxnat/
The PyXNAT page has a tutorial located here: https://pythonhosted.org/pyxnat/tutorial.html
Users on TACC can access XNAT directly using setup_subject.
Run:
module use /work/IRC/opt/modules
module load irc_python
module load setup_subject
Create a directory to work under, for example I might do:
cd $WORK
mkdir mystudy
then by calling setup_subject like this:
setup_subject.py --xnat-project <your project ID> --getdata --keepdata -b . --studyname mystudy -s <your subject's id>
This will access and download your scans automatically.