I am working in slicer 5.9.0 (though I have also used 5.8.0) and I am trying to export PET Segmentations to DICOM. I did not have luck using CLI to export segmentations or the PET labelmap. I have the SlicerRT extension, but I seem to be missing the DICOMSegmentationPlugin. When I try to use the DICOM Export feature, the only export type options I see are Scalar Volume, RT, and Slicer data bundle, not SEG. If anyone is able to advise me in this matter I would greatly appreciate it.
The DICOM Segmentation Object support is in the Quantitative Reporting extension. Please install that and try again.