Review of ionizing radiation Flashcards
T/F?
Some types of radiation produce damage in biologic tissue, whereas others do not. (i.e. artificial lights)
True
What are the 2 Sources of radiation?
- Natural
- Manmade
What are 3 examples of natural radiation?
- Terrestrial radiation (e.g., radon)
- Cosmic radiation (solar and galactic)
- Internal radiation from radioactive atoms (also called radionuclides)
What are 5 examples of manmade radiation?
- Consumer products containing radioactive material
- Air travel
- Nuclear fuel for generation of power
- Atmospheric fallout from nuclear weapons testing
- Nuclear power plant accidents
What are 2 examples of terrestrial radiation? How is can it get into the body?
- Decay of radioactive materials in the earth (soil, water, vegetation)
-Internal or through skin
What does cosmic radiation come from? What type of radiation is it typically?
-From space (stars)
-Typically gamma rays and beta
What is internal radiation due to?
Ingestion, Inhalation, or natural decay of radioactive materials inside the body
What are examples of internal ingested radiation?
Uranium, thorium
What is an example of natural inhaled radiation?
Uranium
What are examples of internal natural radiation within the body?
K-40, Carbon-14
Where does radon gas typically come from?
Radon gas can come in through the basement (any crack or opening)
What are some examples of man made consumer products with radiation?
Tobacco, building materials, older televisions, airport x ray systems, smoke detectors, construction materials
How much radiation is typically emmitted from nuclear power plants?
Small amounts of radioactive gases and liquids
What form of radiation contributes most to dose now days?
Medical radiation
What is the highest source of medical radiation?
CT
What percentage of CT accounts for radiation dose?
65.2%
What percentage does general Radiography account for dose?
8.7%
What percentage does Nuclear Medicine account for dose?
17.4%
What percentage do interventional proceedures account for dose?
8.7%
What are the two largest sources of artificial radiation?
- Diagnostic medical x-ray
- Nuclear medicine procedures
T/F?
We are unable to control natural background radiation; however, exposure from artificial sources must be limited to protect the general population from further biologic damage
True
What is the ONLY source of radiation that we can control?
Medical radiation
When describing the amount of radiation that an individual recieves, what system do we use? What does this system do?
The BERT system; it emphasizes that radiation is an innate part of our environment
Define Energy:
The ability to do work— to move an object against resistance
What type of energy is radiation?
Kinetic energy
What are the 2 catagories of ionizing radiation?
- Electromagnetic radiation
- Particulate radiation
Define ionization?
Conversion of atoms to ions
What is the mass of an x-ray and gamma photon
Has no mass
What is the charge of an x-ray and gamma photon?
Has no charge
How are electromagnetic waves classified?
- Frequency
- Wavelength
What is wave-particle duality?
This form of radiation can travel through space in the form of a wave but can interact with matter as a particle of energy.
What are some examples of particulate radiation?
Alpha particles, beta particles, neutrons, and protons
T/F?
No ionization occurs when the subatomic particles are at rest
True
What elements are alpha particles emmitted from?
Elements such as uranium and plutonium during the process of radioactive decay
What subatomic particles does an alpha photon contain?
2 protons
2 neutrons
What is the mass and charge of an alpha particle?
Have a large mass (approximately 4 times the mass of a hydrogen atom) and a positive charge twice that of an electron
T/F?
Alpha particles can cause a lot of damage in a small amount of time
True
T/F?
Alpha particles are more penetrating than beta particles.
False; Alpha particles are less penetrating than beta particles (fast electrons).
What type of radiation is the least penetrating? Why is this?
-Alpha particles
-They lose energy quickly as they travel a short distance in biologic matter (i.e., into the superficial layers of the skin)
When do alpha particles become dangerous?
As an internal source of radiation, they can be very damaging since they are absorbed in the relatively radiosensitive epithelial tissue
Where are beta particles emmitted from?
Emitted from the nucleus of a radioactive atom during decay
What is the weight of a beta particle compared to an alpha particle?
Beta particle is 8000 times light than an alpha particle
What are the subatomic particles of a beta particle?
Only has one unit of charge (-1)
What interacts with tissue more; alpha particles or beta particles? Why not the other one?
Alpha; because beta particles have attributes such as a charge of -1 and light weight that allows them to penetrate more than alpha particles with far less ionization in thier path.
Why are tungsten, and tungsten rhenium used as target materials in the x-ray tube?
- High melting points
- High atomic numbers
When is charectristic radiation produced?
Characteristic x-rays are produced after ionization of a K-shell electron. When an outer shell electron fills the vacancy in the K shell, an x-ray is emitted.
How is Bremms radiation produced?
Bremsstrahlung x-rays result from the interaction between a projectile electron and a target nucleus. The electron is slowed, and its direction is changed.
T/F?
Not all photons in a diagnostic x-ray beam have the same energy.
True
What is exposure?
Amount of charge created/kg of air by the x-ray beam
What is the SI unit for exposure?
Coulomb per kilogram (C/kg)
What is the conventional unit for exposure?
Roentgen (R) or milliroentgen (mR)
Why bother with a unit that deals with radiation traveling through air? (i.e. meausring using exposure)
A number of dosimetric measurements can take place quite easily in air to represent what might be happening in the human body since the atomic number of air, soft tissue and muscle are simular.
What is air kerma used to express?
Used to express how much energy is transferred/deposited from x-rays to air (how much E deposited into medium of air)
What is kerma?
Total kinetic energy released in a unit mass (kg) of air
What is the SI Unit for air kerma?
gray (Gy) = J/kg
T/F?
Kerma and absorbed dose are basically the same at the diagnostic x-ray level
True
What is dose area product? (DAP)
Sum of the total Air Kerma (energy delivered to patient) over the exposed surface area of the patient.
How is DAP expressed?
Expressed using Gy-cm2 or mGy-cm2
If a patient receives an Air Kerma dose of 20 mGy over a surface area of 100 cm2, what is the dose area product?
2000 mGy-cm2
Where is the DAP meter located, and what is its function?
-Measured through the DAP meter built into the collimator
-Calculates the sum of the air kerma times the surface area
T/F?
Exposure is the baseline quantity from which other dose units are derived.
False; absorbed dose is
What does absorbed dose measure?
Absorbed dose measures the mean amount of energy that is deposited to a medium.
Mass divided by ionizing radiation
What is the SI unit for absorbed dose?
Gy (joule per kg (J/kg))
What is the conventional/older unit for absorbed dose?
rad
What does 1 J/kg equal in rads? What about in Gy?
1 J/kg = 1 Gy = 100 rads
What is Kair of 1 mGy equal to in absorbed dose?
1mGy of Absorbed Dose
T/F?
Absorbed dose does differentiate between different types of radiation
False; Absorbed dose does not differentiate between different types of radiation
What is the SI unit(s) for Equivalent dose?
- SV/mSv
- 1J/kg
What is the non SI unit for equivalent dose?
Rem
What is 1 rem in Sv?
1 rem=.01 SV
What is the radiation weighing factor? (WR)
It is a dimensionless factor used for radiation protection purposes to account for differences biologic impact amoung various tupes of ionizing radiation
(Places risks assosiated with biologic effects on a common scale)
T/F
Equal absorbed doses of different types fo radiation produce different amounts of biologic damage in body tissue.
True
What is the equation for equivalent dose?
EqD=D x WR
What is equivalent dose a product of?
The absorbed dose (Gy) in a tissue and its radiation weighing factor (WR)
T/F
Effective dose takes into consideration the radiosensitivity of the tissue and the effect of the type or radiation through the use of appropriate weighing factors
True
What were 3 consequences of excessive exposure for early pioneers in radiation?
- Radiodermatitis
- Cancer
- Blood disorders
What are 3 early deterministic somatic effects of ionizing radiation?
- Nausea
- Fatigue
- Blood disorders
What are 3 late deterministic somatic effects of ionizing radiation?
- Reduced fertility
- Fibrosis
- Cataract formation
What are 2 late stoctastic effects of ionizing radiation?
- Cancer
- Genetic (hereditary) effects
What is absorbed dose?
The amount of energy absorbed per unit mass
Why do we need effective dose?
We need a measuremtnt that takes into consideration the differing sensitivities of tissues, which equivalent dose lacks.
What is the term that describes the difference in biological response in the breast compared to the shoulder?
Radio sensitivity
What is effective dose?
It is the tissue-weighted sum of the equivalent doses in all specified tissues and organs of the human body and represents the stochastic health risk to the whole body
What does effective dose help determine?
The overall harm to biologic componenets for risk of developing a radiation-induced cancer or for the reproductive organs, the risk of genetic damage
What are the SI units for effective dose?
- J/Kg
- Sv/mSv
What is the conventional unit for effective dose?
Rem
What is the equation for effective dose (Efd)?
EfD=DxWRxWT
What is the equation to find the Sv for effective dose?
Sv=GY x WR x WT
What is the tissue weighting factor (WT)
Takes into account the carcinogenic sensitivity of each organ
If the lungs receive an absorbed dose of .5Gy from exposure to an alpha radiation, what is the effective dose in Sv? The WR is 20 and the tissue weighting factor is .12.
.5 x 20 x .12=1.2 SV
What are the different quantities of all types of radiation?
(List all ways to measure radiation)
- Exposure
- Air kerma
- Absorbed dose
- Eqivalent dose
- Effective dose
What is 1R in C/Kg?
1 R= 2.58x10^4 C/Kg
What is 1 Gy in R?
1Gy=115 R
If x-rays enter a material such as human tissue they may do what?
- Interact with the atoms of the biologic material in the patient
- Pass through without interaction
What is the diagnostic radiology range?
23-150 kVP
What is the most important mode of interaction between x ray photons and the atoms of the patients body?
Photoelectric absorption
T/F
As absorption increases, so does the potential for biologic damage
True
What does photoelectric absorption depend on?
- Energy of photons
- Density of material
- Thickness of material
- Atomic number of material
