National Drug Data File	Radiation Oncology Structures Ontology	Source
http://purl.bioontology.org/ontology/NDDF/006640	urn:absolute:RadiationOncologyStructuresOntology#Testis	LOOM
http://purl.bioontology.org/ontology/NDDF/002128	urn:absolute:RadiationOncologyStructuresOntology#Thyroid	LOOM