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# interfaces.slicer.legacy.diffusion.denoising

## DWIUnbiasedNonLocalMeansFilter

Link to code

Wraps command **DWIUnbiasedNonLocalMeansFilter **

title: DWI Unbiased Non Local Means Filter

category: Legacy.Diffusion.Denoising

description: This module reduces noise (or unwanted detail) on a set of diffusion weighted images. For this, it filters the images using a Unbiased Non Local Means for Rician noise algorithm. It exploits not only the spatial redundancy, but the redundancy in similar gradient directions as well; it takes into account the N closest gradient directions to the direction being processed (a maximum of 5 gradient directions is allowed to keep a reasonable computational load, since we do not use neither similarity maps nor block-wise implementation). The noise parameter is automatically estimated in the same way as in the jointLMMSE module. A complete description of the algorithm may be found in: Antonio Tristan-Vega and Santiago Aja-Fernandez, DWI filtering using joint information for DTI and HARDI, Medical Image Analysis, Volume 14, Issue 2, Pages 205-218. 2010. Please, note that the execution of this filter is extremely slow, son only very conservative parameters (block size and search size as small as possible) should be used. Even so, its execution may take several hours. The advantage of this filter over joint LMMSE is its better preservation of edges and fine structures.

version: 0.0.1.$Revision: 1 $(alpha)

documentation-url: http://wiki.slicer.org/slicerWiki/index.php/Documentation/4.1/Modules/UnbiasedNonLocalMeansFilterForDWI

contributor: Antonio Tristan Vega (UVa), Santiago Aja Fernandez (UVa)

acknowledgements: Partially founded by grant number TEC2007-67073/TCM from the Comision Interministerial de Ciencia y Tecnologia (Spain).

Inputs:

    [Mandatory]
    terminal_output: ('stream' or 'allatonce' or 'file' or 'none')
            Control terminal output

    [Optional]
    args: (a string)
            Additional parameters to the command
    environ: (a dictionary with keys which are a value of type 'str' and with values which
             are a value of type 'str', nipype default value: {})
            Environment variables
    hp: (a float)
            This parameter is related to noise; the larger the parameter, the more agressive the
            filtering. Should be near 1, and only values between 0.8 and 1.2 are allowed
    ignore_exception: (a boolean, nipype default value: False)
            Print an error message instead of throwing an exception in case the interface fails to
            run
    inputVolume: (an existing file name)
            Input DWI volume.
    ng: (an integer)
            The number of the closest gradients that are used to jointly filter a given gradient
            direction (a maximum of 5 is allowed).
    outputVolume: (a boolean or a file name)
            Output DWI volume.
    rc: (an integer)
            Similarity between blocks is measured using windows of this size.
    re: (an integer)
            A neighborhood of this size is used to compute the statistics for noise estimation.
    rs: (an integer)
            The algorithm search for similar voxels in a neighborhood of this size (larger sizes
            than the default one are extremely slow).

Outputs:

    outputVolume: (an existing file name)
            Output DWI volume.