Chapter 4: Radiation Biology Flashcards
ionization
is produced through the photoelectric effect of Compton scatter and results in the formation of a positive atom and a dislodged negative ion
roentgen
- measure of radiation based on the amount of ionization occurring in air
- 1 R= ≈2 billion (2.08 x 10^9) ion pairs in 1 cubic sm (cm^3) of air
- does not describe the amount of radiation absorbed by matter.
exposure rate
dose of exposure/unit of time
Radiation Absorbtion Dose (RAD)
- traditional unit of measuring the amount of radiation energy absorbed by matter
- 1 rad = 100 ergs of energy per gram of tissue (100erg/g)
Roentgen Equivalent Man (REM)
- Traditional unit of measurement used to compare BIOLOGICAL effects of different kinds of radiation in the human body
- multiply rad by a weighted constant specific to the type of radiation
Curie (Ci)
traditional unit of radioactivity 1 Ci = 3.7 x 10^10 decays per second
Gray (Gy)
- SI equivalent to rad (amount of energy absorbed by the tissue)
- 1 Gy = 100 rads
Sievert (Sv)
- SI equivalent to rem (biological effects of radiation)
- 1 Sv = 100 rems
Becquerel (Bq)
- SI equivalent to curie (measure of radioactivity)
- = 1 nucleus decay per second
- 1 Ci = 3.7 x 10^10 Bq
true or false; any dose of radiation, no matter how small, may have a biological effect
true
true or false; biological effects are caused by all types of ionizing radiation
true
direct theory
suggest that cell damage results when ionizing radiation directly hits critical areas, or targets, within the cell
indirect theory
suggests that x-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell
critical organ
an organ that, if damaged, diminishes the quality of a person’s life. Critical organs exposed during dental imaging procedures in the head and neck region include the following:
- thyroid gland
- bone marrow
- skin
- lens of the eye
Linear Energy Transfer (LET)
Amount of energy that an ionizing particle transfers to a material as it travels over a distance
Does higher LET or lower LET confer more biological effects?
higher LET
higher LET radiations
- alpha particles
- protons
- neutrons
lower LET radiations
- electrons
- positrons
- gamma rays
- x-rays
radiation weighting factor (Wr)
- Formerly Quality Factor
- value specific to each radiation type
- used to determine the equivalent dose for uniform whole-body exposure
tissue weighting factor (Wt)
- value specific to the sensitivity of each tissue type
- used to determine effective dose based on individual organs/tissue exposed
somatic effects
- are seen in a person who has been irradiated
- non-reproductive cells
- the exposed organism becomes ill but no genetic transmission
genetic effects
- are not seen in the irradiated person but are passed on to future generations
- no illness in organism
- damage in the next generation
name a factor in environmental exposure/contamination
low-level radiation exposure
MPD
“maximum permissible dose”, maximum dose equivalent that a body is permitted in a specific period.
