Is there a method to import a contoured CT image (dicom file, Varian eclipse) with structures(Target, OAR) to 3D slider program? I want to bring back the structure that Eclipse drew.
Yes, the SlicerRT extension provides the radiation therapy related functions for Slicer.
http://slicerrt.github.io/
You can find the documentation here.
Also there are a huge number of posts in all kinds of related topics here in the forum, so please feel free to use the search function if you have any questions.