General concept
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.. toctree::
   :maxdepth: 1
   :numbered:

   getting_started
   defining_a_geometry
   materials
   setting_up_the_physics
   cut_and_variance_reduction_technics
   source_and_particle_management
   voxelized_source_and_phantom
   tools_to_interact_with_the_simulation_actors
   how_to_run_gate
   visualization