Flashcards in Quiz 1 Deck (112)
What is the definition of radiation?
It is the transmission of energy through space and matter.
It can be ionizing or non-ionizing depending on the amount of energy in the radiation.
Which type of radiation is considered ionizing?
UV rays, x-rays, and gamma rays
What is the definition of ionizing radiation?
Radiation with sufficient energy to displace atomic electrons. It can lead to cell death and molecular alteration
What constitutes the largest percentage of natural radiation?
Radon radiation at 37%
What constitutes the largest percentage of man-made radiation?
CT scans 24%, medical x-rays and nuclear medicine 12%
What are the two types of ionizing radiation? And what kind of cells/particles belong in them?
Particulate Radiation - Alpha, beta particles, and neutrons
Electromagnetic radiation (photons) - gamma and x-rays
! Which of the following is not a form of ionizing radiation?
! A) xrays
! B) microwaves
! C) gamma rays
! D) ultraviolet wavelength light
In terms of units of measurement for radiation, which type is used on boards?
(besides SI units, there are traditional units and you can convert between the two)
What are the units for radiation exposure?
What are the units for absorbed dose?
What are the units for equivalent dose, and effective dose?
What are the units for radioactivity?
What does the measurement of radioactivity tell us?
It tells us the decay rate of a radioactive material. Measured in Bq
What is the definition of radiation exposure?
It is a measurement of radioactive kinetic energy emitted from a source, and is quantified generally by its capacity to ionize air. It's measured in C/kg
What is the definition of air kerma?
The amount of electrical charge produced by ionizing radiation per mass of air. Has to do with radiation exposure because it is measured in C/kg
What is absorbed dose?
It is the energy absorbed by any type of matter, and is derived by calculating the imparted energy divided by the mass absorbing it. Units are Gy, or greys
What is equivalent dose?
It is used to compare the biologic effect on a tissue from different types of radiation. Units are Sieverts (Sv). Equivalent dose is dependent on Linear Energy Transfer (LET), which varies depending on the type of radioactive energy. Particulate radiation has higher LET than photons, thus a greater biologic effect.
What is effective dose?
It is used to measure the estimated risk to humans. Units are Sieverts (Sv). It takes into account the effects of different types of radiation and radiosensitivity of different tissues.
Which tissues are most sensitive, or in other words, which tissues have the highest weighting factor, which is used to calculative effective dose?
The reason we may wish to cover the reproductive organs of a patient when taking radiographs can best be explained by the concept of:
A) Equivalent Dose
B) Linear Energy Transfer (LET)
C) Effective Dose
What is the definition of radiobiology?
The study of the effects of ionizing radiation on living systems
When it comes to radiation chemistry, what is a direct effect?
When a photon or secondary electron ionizes biologic macromolecules.
Photon + RH = R* + H* + e-
The free radicals can then go on to cause havoc
Direct Effect accounts for 1/3 of biologic damage from x-rays. (more common effect with particulate radiation)
Altered molecules have different chemical and biologic properties that may lead to cell death, mutation or carcinogenesis
When it comes to radiation chemistry, what is the radiolysis of water?
It is a photon absorbed by water in an organism, which ionizes water molecules into free radicals.
Photon + H20 = H* + OH*
And these free radicals can join O2 to form hydrogen peroxide and hydroperoxyl and cause damage
When it comes to radiation chemistry, what is an indirect effect?
This is free radicals and toxins produced through the intermediate step of water radiolysis that interact with biologic macromolecules to cause changes. For example, Hydrogen and hydroxyl free radicals are formed from radiolysis of water, which then interact with organic molecules
RH + OH. = R. + H2O
Indirect Effect involves radiolysis of water as precursor to biologic damage, and accounts for 2/3 of biologic damage from x-rays.
What is the primary cause of radiation-induced cell death?
Damage to the DNA. This happens due to breakage of one or both DNA strands, cross-linking, change or loss of base
The presence of which of the following does not contribute to the indirect effect of ionizing radiation on altering DNA?
! A) water (H2O)
! B) oxygen (O2)
! C) photons
! D) hydrogen peroxide (H2O2)
When it comes to classification of cellular changes, what is the deterministic effect?
Radiation injury is dependent on the dose.
Requires higher level of exposure to produce clinically observable effect.
There is an exposure threshold below which the effect does not occur or is not observable.
Deterministic effects are generally tissue-related.
Fibrosis and hematopoietic damage are clinical manifestations.
Where are short term effects of radiation seen?
In tissues that have rapidly dividing cells, like the mouth, GI tract, and bone marrow.
Where are long-term effects of radiation seen?
Loss of parenchymal cells and replacement by fibrous connective tissue. Loss of capillary function so loss of oxygen transport, waste removal, and nutrient transfer