The unit of absorbed dose, symbol Gy, defined as 1 joule per kilogram and equal to 100 rad. Whole-body doses of a few gray delivered quickly cause acute radiation syndrome, and around 4 to 5 Gy without medical treatment is lethal to about half of those exposed. Doses in protection work are so much smaller that milligray and microgray, or the weighted sievert, are the usual units.
Dosimetry lab reconstructs about 1.2 gray to the hand from the source, refer him for a medical evaluation.
Also heard as
- Gy
Do not mix it up with
- Sievert: Gray measures physical energy deposited; sievert weights that energy for radiation type and tissue sensitivity to reflect harm.
Related terms
Absorbed dose
The energy deposited by ionising radiation per unit mass of material, measured in gray.
Sievert
The SI unit for equivalent and effective dose, used to express radiation risk to people.
Deterministic effects
Radiation injuries that appear only above a threshold dose and become more severe as dose increases.
Rem
The US customary unit of dose equivalent, equal to one hundredth of a sievert.