def to_dcm
      # Use the original DICOM object as a starting point (keeping all non-sequence elements):
      #@dcm[REF_FRAME_OF_REF_SQ].delete_children
      @dcm[STRUCTURE_SET_ROI_SQ].delete_children
      @dcm[ROI_CONTOUR_SQ].delete_children
      @dcm[RT_ROI_OBS_SQ].delete_children
      # Create DICOM
      @rois.each do |roi|
        @dcm[STRUCTURE_SET_ROI_SQ].add_item(roi.ss_item)
        @dcm[ROI_CONTOUR_SQ].add_item(roi.contour_item)
        @dcm[RT_ROI_OBS_SQ].add_item(roi.obs_item)
      end
      return @dcm
    end
def to_dcm
      # Use the original DICOM object as a starting point (keeping all non-sequence elements):
      #@dcm[REF_FRAME_OF_REF_SQ].delete_children
      @dcm[STRUCTURE_SET_ROI_SQ].delete_children
      @dcm[ROI_CONTOUR_SQ].delete_children
      @dcm[RT_ROI_OBS_SQ].delete_children
      # Create DICOM
      @rois.each do |roi|
        @dcm[STRUCTURE_SET_ROI_SQ].add_item(roi.ss_item)
        @dcm[ROI_CONTOUR_SQ].add_item(roi.contour_item)
        @dcm[RT_ROI_OBS_SQ].add_item(roi.obs_item)
      end
      return @dcm
    end
Converts the structure set instance to a DICOM object.

 @note This method uses the original DICOM object of the structure set,
   and updates it with attributes from the structure set instance.
 @return [DICOM::DObject] the processed DICOM object