.. _extracting-specific-labels:

Extracting specific labels for registration
###########################################

Following the recommendations from the :ref:`previous page<how-many-labels>`, we can use ``sct_label_utils`` to create a new label image containing just 2 of the vertebral levels.

.. code:: sh

   sct_label_utils -i t2_seg_labeled.nii.gz -vert-body 3,9 -o t2_labels_vert.nii.gz

:Input arguments:
   - ``-i`` : Input image containing a spinal cord labeled with vertebral levels
   - ``-vert-body`` : The top and bottom vertebral levels to create new single-voxel labels for. The labels will be centered within the vertebral body. Choose labels based on your region of interest. Here, we have chosen ``3,9``, indicating C3 to T1 as our region of interest.
   - ``-o`` : Output filename

:Output files/folders:
   - ``t2_labels_vert.nii.gz`` : Image containing 2 single-voxel vertebral labels, centered within the C3 and T1 vertebral bodies.

Once the command has finished, if you have ``fsleyes`` installed, at the bottom of your terminal there will be instructions for inspecting the results using :ref:`fsleyes-instructions`. However, because the output labels are single-voxel, you may need to use zoom to see them clearly in FSLeyes.

.. figure:: https://raw.githubusercontent.com/spinalcordtoolbox/doc-figures/master/vertebral-labeling/io-sct_label_utils.png
   :align: center

   Input/output images for ``sct_label_utils``