Thank you for all the answers.
I am pushed to use DCMTK library by now, but in case there was any high level solution implemented in ITK, I would prefer using it.
The idea for the moment is to store segmentations from multiple stages of treatment. Prefered way to store them is single DICOM image.
So far I am using CT image SOP class with secondary image tag, but this doesnt seem to be the best way.