mrtrix-mime.xml

<?xml version="1.0"?>
 <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>

   <mime-type type="application/x-mrtrix">  
     <comment>MRtrix image</comment>
     <generic-icon name="x-mrtrix"/>
     <magic>
       <match type="string" offset="0" value="mrtrix image"/>
     </magic>
     <glob pattern="*.mif"/>
     <glob pattern="*.mih"/>
   </mime-type>

   <mime-type type="application/x-mrtrix-gz">  
     <comment>MRtrix image (compressed)</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.mif.gz"/>
   </mime-type>

   <mime-type type="application/x-nifti">  
     <comment>NIfTI image</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.nii"/>
   </mime-type>

   <mime-type type="application/x-nifti-gz">  
     <comment>NIfTI image (compressed)</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.nii.gz"/>
   </mime-type>

   <mime-type type="application/x-image-mgh">  
     <comment>MGH image</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.mgh"/>
   </mime-type>

   <mime-type type="application/x-image-mgz">  
     <comment>MGH image (compressed)</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.mgz"/>
   </mime-type>

   <mime-type type="application/x-image-analyze">  
     <comment>Analyze image</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.img"/>
   </mime-type>

   <mime-type type="application/x-mrtrix-tracks">  
     <comment>MRtrix streamlines file</comment>
     <generic-icon name="x-mrtrix"/>
     <glob pattern="*.tck"/>
   </mime-type>

 </mime-info>