Lexicon · NucLex for innovators
Radionuclide
Fully specified name: Radionuclide (concept)
A nuclide with an unstable nucleus that undergoes radioactive decay.
- Scope note
- Its identity is distinct from its molecular formulation.
- Synonyms
- None recorded as true synonyms in this context.
- Monograph
- Radiopharmaceutical identity (planned; brief only)
- External mappings
- None recorded. In W0 no mapping to SNOMED CT® or any external authority is asserted for this entry. A future mapping record will carry source system, identifier, version, relation type, evidence, author, confidence where meaningful, and review state.
- Formal status
- Editorial entry only. It is not part of any released ontology and a prose edit here changes no formal definition.
Draft. This entry is an unreviewed draft. Its sources have not been checked by a named person and no domain reviewer has approved it. Treat every claim as provisional.
Notes
A nuclide is a species of atomic nucleus defined by its number of protons and neutrons, and in some cases by its nuclear energy state. A radionuclide is a nuclide that is unstable and decays, emitting radiation such as alpha particles, beta particles, positrons, gamma rays, or conversion and Auger electrons. The decay mode, the energies emitted, and the half-life are properties of the radionuclide itself and do not change when the atom is attached to a molecule.
That independence is the reason the ontology keeps radionuclide and radiopharmaceutical as separate concepts. The same radionuclide may appear in many agents with very different biological behavior, and the same targeting molecule may be labeled with different radionuclides for imaging or for therapy. A physicist thinking about absorbed dose cares first about the radionuclide; a biologist thinking about where the agent goes cares first about the molecule; a clinician cares about the combination as administered.
Naming conventions vary. Physics texts write the mass number before the element symbol, clinical documents often write the element name followed by the mass number, and product labels follow regulatory conventions. These are names for one concept and belong in a synonym record, not as separate concepts. Formal identifiers for individual nuclides exist in external authorities and are not guessed here.