Radiation Biology Flashcards
Energy that comes from a
source and travels through
space and may be able to
penetrate various materials
Energy released in the form of
particle or waves
radiation
Enough energy to remove tightly bound electrons from the orbit of an atom
- charged or ionized
ionizing radiation
sources of ionizing radiation -
% of naturally occuring
% of artificial
52% of naturally occuring
48% of artificial
Radon, cosmic, internal radionuclides, terrestrial make up what kind of ionizing radiation
naturally occurring (background radiation)
cosmic radiation doubles every _______ feet
6,000
What type of source of ionizing radiation
Nuclear medicine
Interventional radiology
Conventional radiography
Consumer products
Dental
Artificial
What % of dental is an artificial source of ionizing radiation
2.6%
All ionizing radiations produce
biologic changes in ______ tissues
living
What kind of scattering?
Low energy incident photon
Energy is well below the binding energy of the electron
coherent scattering
What kind of scattering?
Change of direction (scatter) of the photon
Minimal impact on image degradation
No ionization – no biological effect
coherent scattering
what kind of absorption?
Electron absorbs all the energy
- ionization
photoelectric absorption
Part of the energy is absorbed by electron –> ejected
- ionization
Scattered photon will have a different direction and wavelength (lower energy)
Compton scattering
Direct hit of critical areas within the cell (e.g. DNA)
Less than 1/3 of effects
direct effects of x-rays on biological macromolecules
Radiation is absorbed by water; molecules are ionized
and form free radicals that damage biological molecules
within the cell (including DNA)
indirect effects of x-rays on biological macromolecules
Breakage of a single DNA strand = Usually ____ biologic consequence
little
Biological effects of radiation - definition?
Severity increases as the absorbed dose increases
deterministic
Biological effects of radiation - definition?
Probability increases as the absorbed dose increases
stochastic
______ and ______ increases as the absorbed dose increases
Severity ; probability
Definition = ______ effects
Radiation exposure exceed a threshold dose
Related to lethal DNA damages
Related to high doses
deterministic effects
Definition = ______ effects
Sublethal radiation-induced damage to DNA
Radiation-induced cancer (and heritable effects)
stochastic effects
Dose
Dose rate
Radiosensitivity
Age
Modifying factors
the relative susceptibility of cells, tissues, organs or
organisms to the harmful effect of ionizing radiation
radiosensitivity
Radiosensitivity is ______ proportional to the mitotic activity and ______ proportional to the degree of differentiation of its cells
directly ; inversely
what does the following:
increase mitosis rate
increase radiosensitivity
decrease differentiation/maturation
radiosensitivity
What kind of radiosensitivity:
Lymphoid organs
Bone marrow
Testicles (germ cells)
Intestines
Mucous membranes
HIGH
What kind of radiosensitivity:
- Fine vasculature
- Growing cartilage
- Growing bone
- Salivary glands
- Thyroid gland
- Lungs
- Kidney
- Liver
INTERMEDIATE
What kind of radiosensitivity:
Mature erythrocytes
Muscle cells
Neurons
LOW
Younger patients = _____ risks because of
Radiosensitivity of cells
More time to develop radiation-induced cancer
higher
