There are specific DICOM standards, in the form of RT DICOM objects, to address the specific needs for Radiation Therapy.

RT Structure Set:  This DICOM object contains information related to patient anatomy, for example, structures, markers, and isocenters.  These entities are typically identified on devices such as CT scanners, physical or virtual simulation workstations, or treatment planning systems.  Often, these are overlays, which can be generated automatically, but mostly through human interaction.  It is not uncommon for a user to have to manually trace with a mouse or lightpen certain areas, e.g., an optical nurve in the eye to be avoided with ratiation in each CT slice in a series of 30 images.