# Non Local Spatial and Angular Matching (NLSAM) denoising

[release]: https://github.com/samuelstjean/nlsam/releases
[DOI]: http://dx.doi.org/doi:10.1016/j.media.2016.02.010
[URL]: http://www.sciencedirect.com/science/article/pii/S1361841516000335
[paper]: https://arxiv.org/pdf/1606.07239.pdf
[autodmri_paper]: https://www.sciencedirect.com/science/article/pii/S1361841520301225
[nlsam_data]: https://github.com/samuelstjean/nlsam_data
[spams]: http://spams-devel.gforge.inria.fr/
[rtd]: https://nlsam.readthedocs.io/en/latest/
[koay_bias]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2765718/

The reference implementation for the Non Local Spatial and Angular Matching (NLSAM) denoising algorithm for diffusion MRI.

## Quick links

+ [Source downloads + precompiled binaries](https://github.com/samuelstjean/nlsam/releases)
+ [Example + Usage guide](example/README.md)

You can find the latest documentation and installation instructions over [here](http://nlsam.readthedocs.io/en/latest) with a downloadable version of the documentation [here](https://readthedocs.org/projects/nlsam/downloads).

## How to install

If you have a working python setup already, the next command should give you everything you need.

```shell
pip install nlsam
```

You can also download the datasets used in the paper over [here][nlsam_data].

## Using the NLSAM algorithm

The process is to first transform your data to Gaussian distributed signals if your dataset is
Rician or Noncentral chi distributed and then proceed to the NLSAM denoising part itself.

A quickstart example call would be

```bash
nlsam_denoising dwi.nii.gz dwi_nlsam.nii.gz bvals bvecs -m mask.nii.gz
```

For more fine grained control and explanation of arguments,
have a look at the possible command line options with nlsam_denoising --help

You can find a detailed usage example and assorted dataset to try out in the
[example](example) folder.

## Questions / Need help / Think this is great software?

If you need help or would like more information, don't hesitate to drop me a
line at samuel.st_jean@university, where university needs to be replaced with med.lu.se

## References

The NLSAM denoising algorithm itself is detailed in

> St-Jean, S., Coupé, P., & Descoteaux, M. (2016).
> "[Non Local Spatial and Angular Matching : Enabling higher spatial resolution diffusion MRI datasets through adaptive denoising][paper]"
> Medical Image Analysis, 32(2016), 115–130. [DOI] [URL]

The bias correction framework is a reimplementation of

> Koay, CG, Özarslan, E and Basser, PJ
> [A signal transformational framework for breaking the noise floor and its applications in MRI][koay_bias],
> Journal of Magnetic Resonance, Volume 197, Issue 2, 2009

The automatic estimation of the noise distribution is computed with

> St-Jean S, De Luca A, Tax C.M.W., Viergever M.A, Leemans A. (2020)
> "[Automated characterization of noise distributions in diffusion MRI data.][autodmri_paper]"
> Medical Image Analysis, October 2020:101758. doi:10.1016/j.media.2020.101758

And here is a premade bibtex entry.

    @article{St-Jean2016a,
      author = {St-Jean, Samuel and Coup{\'{e}}, Pierrick and Descoteaux, Maxime},
      doi = {10.1016/j.media.2016.02.010},
      journal = {Medical Image Analysis},
      pages = {115--130},
      title = {{Non Local Spatial and Angular Matching : Enabling higher spatial resolution diffusion MRI datasets through adaptive denoising}},
      volume = {32},
      year = {2016}
      }