{"entity":{"id":"equivalent-dose","kind":"term","name":"Equivalent dose and effective dose (sievert)","aka":[],"tldr":"A way of converting a physical radiation dose into a single number for comparing radiation risk across different types of radiation and different organs. It is used for radiation-protection purposes, not for prescribing cancer treatment doses.","summary":"Equivalent dose (H) adjusts the absorbed dose in an organ or tissue (measured in gray) by a radiation weighting factor (wR) that reflects how biologically damaging a given type of radiation is, compared with photons or beta particles of the same absorbed dose: H_T = sum over R of wR times D_T,R. Current ICRP values are wR = 1 for photons, electrons and beta particles, wR = 2 for protons, and wR = 20 for alpha particles, reflecting alpha particles' much higher biological potency per unit of physical dose. Equivalent dose is expressed in sievert (Sv), the same unit (J/kg) as gray but with a different name to signal that a biological weighting has been applied.\n\nEffective dose (E) goes one step further, multiplying the equivalent dose to each organ by a tissue weighting factor (wT, which sums to 1 across the whole body) that represents that organ's relative contribution to overall cancer and heritable-disease risk from uniform whole-body irradiation, then summing across organs. Effective dose, also in sievert, is the standard quantity used in radiation protection to compare the stochastic (cancer-risk) burden of different exposures, for example a diagnostic PET/CT scan versus natural background radiation.\n\nThese are protection quantities developed by the ICRP for population-level risk management and regulatory dose limits; they are not used to prescribe or evaluate radiopharmaceutical therapy, where the organ-specific absorbed dose in gray (via the MIRD formalism), sometimes adjusted for relative biological effectiveness rather than the fixed regulatory wR, is what guides treatment planning.","asOf":"2026-09-22","links":[{"label":"ICRP: The Use of Dosimetric Quantities in Radiological Protection","url":"https://www.icrp.org/docs/physics_icrp_found_doc_for_web_consult.pdf"},{"label":"ICRPaedia: Absorbed, Equivalent, and Effective Dose","url":"https://icrpaedia.org/Absorbed,_Equivalent,_and_Effective_Dose"}],"tags":[],"related":["absorbed-dose-term","relative-biological-effectiveness"],"indications":[],"sections":[],"technologies":["in-vivo-dosimetry","radioligand-dosimetry"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"dosimetry"},"route":"/terms/equivalent-dose/","neighbours":{"term":[{"id":"absorbed-dose-term","kind":"term","name":"Absorbed dose and the gray (Gy)","route":"/terms/absorbed-dose-term/"},{"id":"linear-energy-transfer","kind":"term","name":"Linear energy transfer (LET)","route":"/terms/linear-energy-transfer/"},{"id":"relative-biological-effectiveness","kind":"term","name":"Relative biological effectiveness (RBE)","route":"/terms/relative-biological-effectiveness/"}],"technology":[{"id":"in-vivo-dosimetry","kind":"technology","name":"In vivo dosimetry and patient-specific quality assurance","route":"/technologies/in-vivo-dosimetry/"},{"id":"radioligand-dosimetry","kind":"technology","name":"Radioligand dosimetry","route":"/technologies/radioligand-dosimetry/"}]}}