Please help me with this simple error for running Qdec: 

- First I try to open qdec: 

qdec &

- Then this occurs: 

Library not loaded: /opt/X11/lib/libGLU.1.dylib

  Referenced from: /Applications/freesurfer/bin/qdec.bin

  Reason: image not found

Abort

Any ideas on how I could fix this? Thanks! 

All the best, 

Alex