What ITV to PTV expansions do you use for free-breathing definitive IMRT for locally advanced NSCLC using CT sim with 4DCT?

This seems like a simple question, but it is not! It is missing something...the concept of the CTV (clinical target volume) is missing within the question. The idea of the CTV is to include microscopic disease within the region receiving full dose. In the case of locally-advanced lung cancer, CTV is...