Chapter 5 Flashcards
(25 cards)
Compton effect
occurs when an x-ray photon collides with an outer-shell electron, causing ionization and scattering of the x-ray photon with reduced energy. (This is the most frequent interaction with dental radiation.)
Thomas scatter
involves low-energy x-ray photons that interact
with an atom, causing it to vibrate and scatter without ionization or
energy loss.
Photoelectric effect
occurs when an x-ray photon is completely
absorbed by an inner-shell electron, causing ionization. This contributes to image contrast but occurs less frequently.
Direct effect
Ionizing radiation directly hits DNA or critical cell targets,
causing immediate damage.
Indirect effect
Ionizing radiation interacts with water molecules, leading to
the formation of free radicals, which then cause cellular damage.
What does radiobiology study?
The study of the effects of ionizing radiation on living organisms, including the mechanisms of radiation-induced damage and the body’s response.
Define the term dose.
The amount of radiation energy absorbed by tissues.
Describe a free radical.
An uncharged molecule with an unpaired electron, making it highly reactive
and capable of causing cellular damage.
What is background radiation?
What contributes to it?
Natural radiation from cosmic rays, the earth’s crust (radon), and internal body sources. It contributes to the majority of annual radiation exposure.
List stochastic radiologic effect.
Effects that occur by chance and increase in probability with dose, such as cancer and genetic mutations, with no threshold dose.
Stochastic Effects
Probability increases with dose but severity is
independent of dose (e.g., cancer).
Deterministic Effects
Severity increases with dose and has a threshold
(skin erythema, cataracts).
What are the direct effects of radiation.
What areas are affected?
Direct damage to DNA or cellular structures.
What are the indirect effects of radiation?
What areas are affected?
Damage from free radicals formed by radiation interacting with water molecules.
List traditional units of radiation.
- Roentgen (R)
- Rad
- Rem
Define latent period.
Time between radiation exposure and the appearance of clinical symptoms.
Define period of injury.
The time when cellular damage is visible or measurable.
Define radioresistant.
Tissues or cells that are less sensitive to radiation (e.g., muscle, nerve cells).
Define radiosensitive.
Tissues or cells that are more sensitive to radiation (e.g., lymphocytes,
bone marrow).
What tissue is considered radiosensitive?
Bone marrow, reproductive cells, and lymphoid tissues.
List critical organs.
Thyroid gland, bone marrow, skin, and eyes.
What is artificial radiation? Sources?
Man-made radiation from medical procedures, nuclear industry, consumer products (examples, CT scans, nuclear power plants)
Human tissue is composed primarily of ___, which affects how the x-ray energy is absorbed.
Water
What surface of caries are most often seen on radiographs?
Proximal surfaces (mesial and distal)
