Units and Quantities

Unit (Symbol)DefinitionUnits
Exposure (X)
Amount of ionization per mass of air due to X-rays and gamma rays.Roentgen (R)
Absorbed Dose (D)
Amount of energy imparted by radiation per unit mass.SI: Gray (Gy)

Traditional: rad
1 rad = 0.01Gy
Kerma (K)
Kinetic Energy Released per unit MAss
Kinetic energy transferred to charged particles per unit mass.
SI: Gray (Gy)

Traditional: rad
1 rad = 0.01Gy
Equivalent Dose (HT)
A measure of absorbed dose weighted for the biological effectiveness
of the types(s) of radiation (relative to the low LET photons and electrons)
to produce stochastic health effects in humans.
SI: Sievert (Sv)

Traditional: rem
1 rem = 0.01Sv
Dose Equivalent (H)
A measure of absorbed dose weighted for the biological effectiveness of
the types of radiation (relative to low LET photons and electrons) to
produce stochastic health effects in humans.
Sievert (Sv)

Traditional: rem
1 rem = 0.01Sv
Effective Dose (E)
A measure of equivalent dose, weighted for the biological sensitivity of
the exposed tissues and organs (relative to whole body exposure) to
stochastic health effects in humans.
Sievert (Sv)

Traditional: rem
1 rem = 0.01Sv
Effective Dose
Equivalent (HE)

A measure of equivalent dose, weighted for the biological sensitivity of
the exposed tissues and organs (relative to whole body exposure) to
stochastic health effects in humans.
Sievert (Sv)

Traditional: rem
1 rem = 0.01Sv

Conversion Factors

Energy

  • \(Joule (J) = Electron Volt (eV) \times 1.602 \times 10^{-19}\)

Radiation Units

  • Air Collision Kerma (Gy)

Temperature

  • Degrees Kelvin (K) = Degrees Celsius (C) + 273.16

Units

Physical Quantity Unit Name Symbol
Charge (electric) Coulomb C
Dose Gray Gy (=J/kg)
Energy Joule J
Energy Electron Volt eV
Exposure Roentgen R
Length Meter m
Mass kilogram kg
Time second s
Time minute min

Metric Unit Prefix

Prefix Symbol Base 10 Decimal
yotta Y 1024 1,000,000,000,000,000,000,000,000
zetta Z 1021 1,000,000,000,000,000,000,000
exa E 1018 1,000,000,000,000,000,000
peta P 1015 1,000,000,000,000,000
tera T 1012 1,000,000,000,000
giga G 109 1,000,000,000
mega M 106 1,000,000
kilo k 103 1,000
hecto h 102 100
deca da 101 10
100 1
deci d 10-1 0.1
centi c 10-2 0.01
milli m 10-3 0.001
micro μ 10-6 0.000,001
nano n 10-9 0.000,000,001
pico p 10-12 0.000,000,000,001
femto f 10-15 0.000,000,000,000,001
atto a 10-18 0.000,000,000,000,000,001
zepto z 10-21 0.000,000,000,000,000,000,001
yocto y 10-24 0.000,000,000,000,000,000,000,001