NucLexNuclear Medicine Lexicon and Theranostics Ontology
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Lexicon entryDraftNX-C040

Dosimetry

Fully specified name: Dosimetry (concept)

The measurement or estimation of absorbed radiation dose.

Scope note
This stub provides no patient-specific dose calculation.
Synonyms
None recorded as true synonyms in this context.
Monograph
Biodistribution and pharmacokinetics (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

Dosimetry is the measurement or estimation of absorbed dose, the energy deposited by ionizing radiation per unit mass of tissue. In nuclear medicine the radiation source is inside the body, so dose is almost never measured directly in a patient; it is estimated from the amount of radioactivity in each region over time, the properties of the radionuclide, and a model of how energy emitted in one region is absorbed in another.

The quantities form a chain. Activity in a region, measured by imaging or counting at several times, is integrated to give cumulated activity. The radionuclide's decay data give the energy emitted per decay. A geometric model, whether a standard phantom or the patient's own anatomy, gives the fraction of that energy absorbed in each target region. Each link has its own assumptions and uncertainty, and the result is only as specific as the weakest link. Formalisms for this chain have been published by the Medical Internal Radiation Dose (MIRD) committee, and protection quantities and reference models by the International Commission on Radiological Protection (ICRP).

Physicists, physicians, and regulators use "dose" differently. Absorbed dose, equivalent dose, and effective dose are distinct quantities with distinct purposes, and the clinician's "dose" often means administered activity. NucLex keeps these apart. This entry describes the concept only. It provides no patient-specific dose calculation and no numerical value for any agent or organ.

Sources consulted (2)
  • International Commission on Radiological Protection (ICRP). Publications on radiation protection quantities and dosimetry. https://www.icrp.org/
  • Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine and Molecular Imaging. Pamphlets on internal dosimetry formalism. https://www.snmmi.org/