Before starting this tutorial ############################# This tutorial is intended to be run following the previous :ref:`gm-wm-segmentation` tutorial, as GM/WM metric computation relies on having segmentation masks of the grey and white matter. You can either run that tutorials first, or download the necessary files below: #. Make sure that you have the following files in your working directory: * ``single_subject/data/t2s/t2s.nii.gz`` : A T2* anatomical image of the spinal region. * ``single_subject/data/t2s/t2s_wmseg.nii.gz``: A binary mask for the white matter segmentation of the spinal cord. * ``single_subject/data/t2s/t2s_gmseg.nii.gz``: A binary mask for the gray matter segmentation of the spinal cord. You can get these files by downloading :sct_tutorial_data:`data_gm-wm-metric-computation.zip`. #. Open a terminal and navigate to the ``single_subject/data/t2s/`` directory: .. code:: sh cd {PATH_TO_DOWNLOADED_DATA}/single_subject/data/t2s/