<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A substance (such as a radioisotope) used in imaging procedures.</n0:def-definition><n0:def-source>NCI-GLOSS</n0:def-source></n0:ComplexDefinition>
<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A substance that is identifiable by virtue of its radioactive signature, color, or other distinguishing physical property, such as a dye, radioactive isotope, or inert chemical, that is introduced into a biological or mechanical system and can be followed through the course of a process, providing information on the pattern of events in the process or on the redistribution of the parts, elements, or events involved.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>