.. _connectome2tck:

connectome2tck
===================

Synopsis
--------

Extract streamlines from a tractogram based on their assignment to parcellated nodes

Usage
--------

::

    connectome2tck [ options ]  tracks_in assignments_in prefix_out

-  *tracks_in*: the input track file
-  *assignments_in*: input text file containing the node assignments for each streamline
-  *prefix_out*: the output file / prefix

Description
-----------

The compulsory input file "assignments_in" should contain a text file where there is one row for each streamline, and each row contains a list of numbers corresponding to the parcels to which that streamline was assigned (most typically there will be two entries per streamline, one for each endpoint; but this is not strictly a requirement). This file will most typically be generated using the tck2connectome command with the -out_assignments option.

Example usages
--------------

-   *Default usage*::

        $ connectome2tck tracks.tck assignments.txt edge-

    The command will generate one track file for every edge in the connectome, with the name of each file indicating the nodes connected via that edge; for instance, all streamlines connecting nodes 23 and 49 will be written to file "edge-23-49.tck".

-   *Extract only the streamlines between nodes 1 and 2*::

        $ connectome2tck tracks.tck assignments.txt tracks_1_2.tck -nodes 1,2 -exclusive -files single

    Since only a single edge is of interest, this example provides only the two nodes involved in that edge to the -nodes option, adds the -exclusive option so that only streamlines for which both assigned nodes are in the list of nodes of interest are extracted (i.e. only streamlines connecting nodes 1 and 2 in this example), and writes the result to a single output track file.

-   *Extract the streamlines connecting node 15 to all other nodes in the parcellation, with one track file for each edge*::

        $ connectome2tck tracks.tck assignments.txt from_15_to_ -nodes 15 -keep_self

    The command will generate the same number of track files as there are nodes in the parcellation: one each for the streamlines connecting node 15 to every other node; i.e. "from_15_to_1.tck", "from_15_to_2.tck", "from_15_to_3.tck", etc.. Because the -keep_self option is specified, file "from_15_to_15.tck" will also be generated, containing those streamlines that connect to node 15 at both endpoints.

-   *For every node, generate a file containing all streamlines connected to that node*::

        $ connectome2tck tracks.tck assignments.txt node -files per_node

    Here the command will generate one track file for every node in the connectome: "node1.tck", "node2.tck", "node3.tck", etc.. Each of these files will contain all streamlines that connect the node of that index to another node in the connectome (it does not select all tracks connecting a particular node, since the -keep_self option was omitted and therefore e.g. a streamline that is assigned to node 41 will not be present in file "node41.tck"). Each streamline in the input tractogram will in fact appear in two different output track files; e.g. a streamline connecting nodes 8 and 56 will be present both in file "node8.tck" and file "node56.tck".

-   *Get all streamlines that were not successfully assigned to a node pair*::

        $ connectome2tck tracks.tck assignments.txt unassigned.tck -nodes 0 -keep_self -files single

    Node index 0 corresponds to streamline endpoints that were not successfully assigned to a node. As such, by selecting all streamlines that are assigned to "node 0" (including those streamlines for which neither endpoint is assigned to a node due to use of the -keep_self option), the single output track file will contain all streamlines for which at least one of the two endpoints was not successfully assigned to a node.

-   *Generate a single track file containing edge exemplar trajectories*::

        $ connectome2tck tracks.tck assignments.txt exemplars.tck -files single -exemplars nodes.mif

    This produces the track file that is required as input when attempting to display connectome edges using the streamlines or streamtubes geometries within the meview connectome tool.

Options
-------

Options for determining the content / format of output files
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

-  **-nodes list** only select tracks that involve a set of nodes of interest (provide as a comma-separated list of integers)

-  **-exclusive** only select tracks that exclusively connect nodes from within the list of nodes of interest

-  **-files option** select how the resulting streamlines will be grouped in output files. Options are: per_edge, per_node, single (default: per_edge)

-  **-exemplars image** generate a mean connection exemplar per edge, rather than keeping all streamlines (the parcellation node image must be provided in order to constrain the exemplar endpoints)

-  **-keep_unassigned** by default, the program discards those streamlines that are not successfully assigned to a node. Set this option to generate corresponding outputs containing these streamlines (labelled as node index 0)

-  **-keep_self** by default, the program will not output streamlines that connect to the same node at both ends. Set this option to instead keep these self-connections.

Options for importing / exporting streamline weights
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

-  **-tck_weights_in path** specify a text scalar file containing the streamline weights

-  **-prefix_tck_weights_out prefix** provide a prefix for outputting a text file corresponding to each output file, each containing only the streamline weights relevant for that track file

Standard options
^^^^^^^^^^^^^^^^

-  **-info** display information messages.

-  **-quiet** do not display information messages or progress status; alternatively, this can be achieved by setting the MRTRIX_QUIET environment variable to a non-empty string.

-  **-debug** display debugging messages.

-  **-force** force overwrite of output files (caution: using the same file as input and output might cause unexpected behaviour).

-  **-nthreads number** use this number of threads in multi-threaded applications (set to 0 to disable multi-threading).

-  **-config key value** *(multiple uses permitted)* temporarily set the value of an MRtrix config file entry.

-  **-help** display this information page and exit.

-  **-version** display version information and exit.

References
^^^^^^^^^^

Tournier, J.-D.; Smith, R. E.; Raffelt, D.; Tabbara, R.; Dhollander, T.; Pietsch, M.; Christiaens, D.; Jeurissen, B.; Yeh, C.-H. & Connelly, A. MRtrix3: A fast, flexible and open software framework for medical image processing and visualisation. NeuroImage, 2019, 202, 116137

--------------



**Author:** Robert E. Smith (robert.smith@florey.edu.au)

**Copyright:** Copyright (c) 2008-2025 the MRtrix3 contributors.

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Covered Software is provided under this License on an "as is"
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See the Mozilla Public License v. 2.0 for more details.

For more details, see http://www.mrtrix.org/.


