⚡ Turboprep

turboprep is a preprocessing script for structural MRIs built on top of awesome open-source tools (the full pipeline is described here). Given an input MRI and a reference space (e.g., the MNI152 template), turboprep outputs an aligned, skull-stripped, and intensity-normalized MRI, along with its segmentation (using SynthSeg) and brain mask.

🆕 Run with Docker!

Installing FreeSurfer and ANTs too much hassle? Run turboprep with Docker! First, make sure you have Docker installed, then run the turboprep-docker script:

./turboprep-docker /path/to/input/file.nii.gz \
                   /path/to/output/directory \
                   /path/to/template/file.nii.gz \
                   [OPTIONS]

On the first run, this will download and install the lemuelpuglisi/turboprep Docker image (~16GB of disk space required).

The script runs turboprep using the cpu to simplify setup and avoid additional steps (e.g., installing the NVIDIA Docker runtime). Despite this, it still achieves a runtime comparable to the GPU version.

Classic installation

turboprep script requires the following softwares to be installed:

• FreeSurfer >= v7.4
• ANTs
• intensity-normalization

A Docker container will be included in the future.

Usage (one input)

=====[ turboprep ]=====
Usage: /usr/bin/turboprep <image_path> <output_folder> <template_path> [OPTIONS]

Options:
  -t, --threads <threads>               Threads (default: number of cores)
  -s, --shrink-factor                   Bias field correction shrink factor (default: 3), see N4BiasFieldCorrection
  -m, --modality <modality>             Modality {t2,other,md,t1,pd,flair} (default is t1)
  -r, --registration-type <type>        Registration type {t,r,a} (default is 'a' (affine), see antsRegistrationSyNQuick.sh)
  --no-bfc                              Skip bias field correction step
  --keep                                Keep intermediate files

Usage (multiple inputs)

usage: turboprep-multiple.py [-h] --inputs INPUTS --outputs OUTPUTS --template TEMPLATE [-m MODALITY] [-t THREADS] [-s SHRINK_FACTOR]
                         [-r REGISTRATION_TYPE] [--no-bfc NO_BFC] [--keep]

options:
  -h, --help            show this help message and exit
  --inputs INPUTS       text file where each line is the path of an image to process
  --outputs OUTPUTS     text file where each line is the path to an output
  --template TEMPLATE   path of template image
  -m MODALITY, --modality MODALITY
                        Modality {t2,other,md,t1,pd,flair} (default is t1)
  -t THREADS, --threads THREADS
                        Threads (default: number of cores)
  -s SHRINK_FACTOR, --shrink-factor SHRINK_FACTOR
                        Bias field correction shrink factor (default: 3), see N4BiasFieldCorrection
  -r REGISTRATION_TYPE, --registration-type REGISTRATION_TYPE
                        Registration type {t,r,a} (default is 'a' (affine), see antsRegistrationSyNQuick.sh)
  --no-bfc NO_BFC       text file listing the inputs for which to skip bias field correction
  --keep                Keep intermediate files

Example of --inputs file:

/path/to/images/input-a.nii.gz
/path/to/images/input-b.nii.gz
/path/to/images/input-c.nii.gz

Example of --outputs file:

/path/to/outputs/input-a/
/path/to/outputs/input-b/
/path/to/outputs/input-c/

Example of --no-bfc file (skip bias-field correction for input-a and input-c):

/path/to/images/input-a.nii.gz
/path/to/images/input-c.nii.gz

Pipeline description

Step n.	Description	Algorithm	Package
0	Intensity inhomogeneity correction	N4 [1]	ANTs
1	Skull stripping	SynthStrip [7]	FreeSurfer
2	Affine registration to template	Symmetric Diffeomorphic Image Registration (just affine registration) [2]	ANTs
3	Segmentation of brain tissues	SynthSeg [3]	FreeSurfer
4	Brain mask extraction	Thresholding the segmentation	FreeSurfer
5	Intensity normalization	WhiteStripe [4]	intensity-normalization

Registration alternatives

Two alternatives powered by deep learning are:

• EasyReg [6] - implemented in FreeSurfer as mri_easyreg
• SynthMorph [7] - implemented in FreeSurfer as mri_synthmorph

Both algorithms are great, but the overhead of loading the model make their running time slower compared to ANTs when performing affine image registration.

Bibliography

[1] Tustison, Nicholas J., et al. "N4ITK: improved N3 bias correction." IEEE transactions on medical imaging 29.6 (2010): 1310-1320.

[2] Avants, Brian B., et al. "Symmetric diffeomorphic image registration with cross-correlation: evaluating automated labeling of elderly and neurodegenerative brain." Medical image analysis 12.1 (2008): 26-41.

[3] Billot, Benjamin, et al. "SynthSeg: Segmentation of brain MRI scans of any contrast and resolution without retraining." Medical image analysis 86 (2023): 102789.

[4] Shinohara, Russell T., et al. "Statistical normalization techniques for magnetic resonance imaging." NeuroImage: Clinical 6 (2014): 9-19.

[5] Iglesias, Juan Eugenio. "A ready-to-use machine learning tool for symmetric multi-modality registration of brain MRI." Scientific Reports 13.1 (2023): 6657.

[6] Hoffmann, M., et al. "SynthMorph: Learning image registration without images." IEEE Trans. Med. Imaging (2021).

[7] Hoopes, Andrew, et al. "SynthStrip: Skull-stripping for any brain image." NeuroImage 260 (2022): 119474.