Lecture 1 - Radiation Flashcards
Radioactivity describes what?
The decay rate of a radioactive material.
*Measured in Becquerels
What is exposure?
Measure of radioactive kinetic energy emitted from a source and is quantified generally by its capacity to ionize air. It’s a measure of the intensity of the radiation field.
*Measured in units of charge/mass - Coulombs/Kilogram (C/Kg)
What is the absorbed dose?
Energy absorbed by any type of matter, and is derived by calculating the imparted energy divided by the mass absorbing it.
*Measured in Gray (Gy)
What is the equivalent dose?
It is used to compare the biological effect on a tissue from diff types of radiation.
*Particulate radiation has high LET (linear energy transfer) than photons, and thus a greater biological effect. [Larger marbles have more mass and can potentially transfer more energy in a collision
**Measured in Sieverts (Sv)
What is the effective dose?
It is used to measure the estimated risk to humans.
*Takes into account the type of radiation (equivalent dose) and the nature of each organ or tissue being irradiated, so sums it up to get a whole body effective dose
**Measured in Sievert (Sv)
More ________ dividing, ______ differentiated cells are most susceptible and thus are more heavily weighted in calculating effective dose.
Rapidly
Less
What is the absorbed dose?
What is the equivalent dose?
What is the effective dose?
- Energy deposited in a kg of a substance by the radiation
- Absorbed dose weighted for harmful effects of different radiations
- Equivalent dose weighted for susceptibility to harm of different tissues (More sensitive the tissue is, the higher the effective dose)
What is radiobiology?
The study of the effects of ionizing radiation on living systems
What is a direct effect?
When a photon or secondary e- ionizes biological macromolecules
THIS ACCOUNTS FOR 1/3 OF BIOLOGIC DAMAGE FROM X-RAYS
T/F - Altered molecules differ structurally and functionally from originals, so this results in a biological change.
TRUE
*Can lead to cell death, mutation, or carcinogenesis
What is the radiolysis of water?
Photon absorbed by water in an organism, ionizing water molecules into free radicals
*photon + H2O = Hdot + OHdot
T/F - Ionization of H2O leads to free radical production.
TRUE
What is the indirect effect?
Free radicals and toxins produced thru the intermediate step of water radiolysis then interact with biological macromolecules to cause changes.
THIS ACCOUNTS FOR 2/3 OF BIOLOGICAL DAMAGE FROM X-RAYS
T/F - Organic free radicals are unstable and transform quickly to stable altered molecules
TRUE
What is the primary cause of radiation induced cell death?
Damage to DNA
Can result from:
Breakage of one or both DNA strands
Cross linking of DNA strands w/in helix to other DNA strands
Change or loss of base
Disruption of H-H bonds b/t DNA strands
What is the deterministic effect?
Radiation injury dependent on the dose
-The greater the dose, the greater the injury severity
High level of exposure is req’d to produce a clinically observable effect
There is an exposure threshold below which the effect does not occur or is clinically observable
Typically these effects are tissue related
What are 4 modifying factors of deterministic effects on tissues and organs?
Dose - above threshold level
Dose rate - High rate produces more damage
O2 - Damage increases as oxygen level rises
LET - Increase LET (Linear energy transfer) produces greater damage
T/F - Less differentiated tissues are more sensitive to radiation.
True
*Stem cells are highly sensitive to radiation
What is the stochastic effect?
This is the one that we really worry about with taking radiographs
Radiation injury is based on the probability of occurrence
Probability of the effect occurring increases with dose
There is no threshold level, and there is not level of exposure at which there is zero risk
Examples: Radiation induced cancer and genetic alterations from sub lethal damage to DNA
What are the 3 guiding principles of radiation safety?
Justification - We have the obligation to do more good than harm
ALARA - As low as reasonably achievable
Dose limitation - There are no dose limits in diagnostic and therapeutic radiology, so we need to adhere to good radiation safety practices and have a good radiation protection program in place
What is radiation?
Transmission of energy through space and matter
*Can be ionizing or nonionizing depending on the amount of energy in the radiation
EX: Heat, light, sound, radio, microwaves
Higher frequency = __________ energy
MORE
Where is the line b/t non-ionizing radiation and ionizing radiation?
B/t visible light and UV radiation. Visible light and lower is non, while UV and higher (X-rays and gamma rays) are ionizing
What is ionizing radiation?
Radiation with sufficient energy to displace atomic electrons, and that breaks bonds that hold a molecule together
*Can lead to cell death and/or molecular alteration leading to harmful effects
We get 50% of our radiation from where/what? What about the other 50%?
Natural - Mostly from radon 37%
Manmade - CT scans 24%
What is particulate radiation?
Alpha and beta particles and neutrons
What is electromagnetic radiation?
Photons
EX: Gamma and X rays
Exposure is measured in what?
Coulomb/kilogram
Absorbed dose (imparted energy/mass) is measured in what?
Gray
Equivalent dose is measured in what?
Sievert
Effective does is measured in what?
Sievert
Radioactivity is measured in what?
Becquerel
What is radiation?
Transmission of energy thru space and matter
What is ionizing radiation?
Radiation with sufficient energy to displace atomic electrons, thus breaking bonds that hold a molecule together
Our sources of radiation come from two main things. What are they?
Natural
Man-made
Tell me the following forms of natural radiation listed from greatest to least.
RADON - 37%
COSMIC - 5%
INTERNAL - 5%
TERRESTRIAL - 3%
Tell me the sources of man-made radiation from greatest to least.
CT Scans - 24%
Medical x-rays - 12%
Nuclear medicine - 12%
Consumer products - 2%
Other - ~1%, Occupational, fallout, nuclear fuel cycle, misc
Particulate radiation has three things. Name them.
Alpha particles
Beta particles
Neutrons
Electromagnetic radiation (photons) have 2 things. Name them.
Gamma rays
X rays
SI Units
Exposure?
Absorbed dose?
Equivalent dose?
Effective dose?
Radioactivity?
Exposure - Coulomb/kilogram (C/kg)
Absorbed - Gray
Equivalent dose - Sievert (Sv)
Effective dose - Sievert (Sv)
Radioactivity - Becquerel (Bq)
