Radiation units Flashcards
What does exposure mean?
Radiation causes ionization of air molecules.
Electric charge is a measure of the amount of ionization.
The total electric charge formed in a give mass of air is known as exposure.
What is the unit of electric charge?
Coulomb (Q)
How do you work out exposure?
Exposure= coulomb/kilogram
Q/M
What does absorbed dose mean?
Energy deposited in the patient
Energy transferred to irradiated material
How is absorbed dose worked out
Joules/kilogram
J.kg⁻¹
What are the units of absorbed dose?
Grey (Gy)
1 grey = 1 J.kg⁻¹
In diagnostic usually expressed as milliGrey
mGy
What is dose equivalent?
Absorbed does doesnt take into account the damage different types of radiation can do.
Dose equivalent takes this into account.
What is the unit of dose equivalent?
Sievert (Sv)
How do you work out dose equivalent?
Dose equivalent (Sv) = Absorbed dose x quality factor GyxQF
The quality factor depends on the type of radiation.
What are the units of radiation?
Exposure
Absorbed dose
Dose equivalent
Effective dose
What is Effective dose?
Effective dose is the unit of energy deposited into the patient relating to the tissues.
Some tissues are more radiosensitive than others.
How do you work out effective dose? and units?
Dose equivalent x weighing factor
Units is sieverts (Sv)
What is the weighting factor?
Weighting factors depend on the type of tissue.
It is how radiosensitive a tissue is.
Higher weighing, higher radiosensitivity/higher damage.
Advantage and disadvantage of effective dose.
Allows us to compare different imaging/RT treatments
Doesnt take into account age e.g child is growing, more risk
What does DLP mean?
Dose length product
Length refers to the area on the patient
