Creating single DICOM file with the segmentation marked on MRI

Operating system: Windows 10
Slicer version: 4.8.1
Expected behavior:
Actual behavior:

I am working with an MRI dataset (3D Sag T1). I wish to segment (a single gyrus) an area using slicer and then change the corresponding voxels on the MRI DICOM images to create a new single DICOM file with the segmented area (a gyrus) appearing in high density/white (on T1 images).
The eventual aim is to create volume rendering which can run on a standard DICOM viewer (without use of slicer) with the segmented area visible separately (marked out) from the rest of the gyri.
Thanks in advance!!