Running HippUnfold with Singularity

Pre-requisities:

1. Singularity or Apptainer is installed on your system. For more info, see the detailed apptainer install instructions.
2. The following command-line tools are installed:
   • wget
   • tar
3. Sufficient disk-space
   • in your /tmp folder (>30GB) to build the container (not needed for dropbox download)
   • in your working folder to store the container (~15GB)
   • for HippUnfold outputs (~4GB per subject)
4. Sufficient CPU and memory - the more you have, the faster it will run, but we recommend at least 8 CPU cores and 16GB memory.

First time setup

Pull the container:

singularity pull khanlab_hippunfold_latest.sif docker://khanlab/hippunfold:latest

Run HippUnfold without any arguments to print the short help:

singularity run -e khanlab_hippunfold_latest.sif

Use the -h option to get a detailed help listing:

singularity run -e khanlab_hippunfold_latest.sif -h

Note that all the Snakemake command-line options are also available in
HippUnfold, and can be listed with --help-snakemake:

singularity run -e khanlab_hippunfold_latest.sif --help-snakemake

Note: If you encounter any errors pulling the container from dockerhub, it may be because you are running
out of disk space in your cache folders. Note, you can change these locations
by setting environment variables, however, using a network file system for the folders may result in poor performance and/or errors e.g.:

export SINGULARITY_CACHEDIR=/YOURDIR/.cache/singularity

Running an example

Download and extract a single-subject BIDS dataset for this test:

wget https://www.dropbox.com/s/mdbmpmmq6fi8sk0/hippunfold_test_data.tar 
tar -xvf hippunfold_test_data.tar

This will create a ds002168/ folder with a single subject, that has a
both T1w and T2w images:

ds002168/
├── dataset_description.json
├── README.md
└── sub-1425
    └── anat
        ├── sub-1425_T1w.json
        ├── sub-1425_T1w.nii.gz
        ├── sub-1425_T2w.json
        └── sub-1425_T2w.nii.gz

2 directories, 6 files

Now let's run HippUnfold.

singularity run -e khanlab_hippunfold_latest.sif ds002168 ds002168_hippunfold participant -n --modality T1w

Explanation:

Everything prior to the container (khanlab_hippunfold_latest.sif) are arguments to singularity, and after are to HippUnfold itself. The first three arguments to HippUnfold (as with any BIDS App) are the input
folder (ds002168), the output folder (ds002168_hippunfold), and then the analysis level (participant). The participant analysis
level is used in HippUnfold for performing the segmentation, unfolding, and any
participant-level processing. The group analysis is used to combine subfield volumes
across subjects into a single tsv file. The --modality flag is a
required argument, and describes what image we use for segmentation. Here
we used the T1w image. We also used the --dry-run/-n option to
just print out what would run, without actually running anything.

When you run the above command, a long listing will print out, describing all the rules that
will be run. This is a long listing, and you can better appreciate it with the less tool. We can
also have the shell command used for each rule printed to screen using the -p Snakemake option:

singularity run -e khanlab_hippunfold_latest.sif ds002168 ds002168_hippunfold participant -np --modality T1w | less

Now, to actually run the workflow, we need to specify how many cores to use and leave out
the dry-run option. The Snakemake --cores option tells HippUnfold how many cores to use.
Using --cores 8 means that HippUnfold will only make use of 8 cores at most. Generally speaking
you should use --cores all, so it can make maximal use of all the CPU cores it has access to on your system. This is especially
useful if you are running multiple subjects.

Running the following command (hippunfold on a single subject) may take ~30 minutes if you have 8 cores, shorter if you have more
cores, but could be much longer (several hours) if you only have a single core.

singularity run -e khanlab_hippunfold_latest.sif ds002168 ds002168_hippunfold participant -p --cores all --modality T1w

Note that you may need to adjust your Singularity options to ensure the container can read and write to yout input and output directories, respectively. You can bind paths easily by setting an
environment variable, e.g. if you have a /project folder that contains your data, you can add it to the SINGULARITY_BINDPATH so it is available when you are running a container:

export SINGULARITY_BINDPATH=/data:/data

After this completes, you should have a ds002168_hippunfold folder with outputs for the one subject.

Exploring different options

If you alternatively want to run HippUnfold using a different modality, e.g. the high-resolution T2w image
in the BIDS test dataset, you can use the --modality T2w option. In this case, since the T2w image in the
test dataset has a limited FOV, we should also make use of the --t1-reg-template command-line option,
which will make use of the T1w image for template registration, since a limited FOV T2w template does not exist.

singularity run -e khanlab_hippunfold_latest.sif ds002168 ds002168_hippunfold_t2w participant --modality T2w --t1-reg-template -p --cores all

Note that if you run with a different modality, you should use a separate output folder, since some of the files
would be overwritten if not.