Sources & Types Flashcards
Cosmic radiation
Extraterrestrial in origin, higher intensity at a higher altitude
Natural/Background Radiation
Cosmic, terrestrial, and internal radiation.
Very little can be done about this.
Terrestrial radiation
Natural products of planet earth, for example radon gas
Radon gas
The largest source of natural radiation exposure
Internal radiation
Natural products found within the human body
Radioactivity
the property possessed by some elements (as uranium) or isotopes (as carbon 14) of spontaneously emitting energetic particles (as electrons or alpha particles) by the disintegration of their atomic nuclei
Man made/artificial radiation
CT, nuclear medicine, interventional fluoroscopy, medical X-ray, consumer products, occupational, industrial, primary medical
Medical radiation
Primary source of man made radiation
CT, nuclear medicine, interventional fluoroscopy, conventional X-ray
Consumer products
Cathode ray tubes, smoke detectors
Industrial
Radiation used in industrial applications
Nuclear fallout
Radioactive debris from nuclear detonations
Leakage radiation
Leaves the tube housing at a point other than the window
Primary radiation
Created in the X-ray tube, proceeds towards the patient
Secondary radiation
Created at a point other than the X-ray tube
Scatter radiation
Primary X-ray redirected due to interaction with matter
Effects of scatter
Bad for the image, carries no anatomical information, adds useless density into the image receptor/image, veil of gray.
Scatter production varies by
X-ray beam field size.
As the area increases, scatter increases.
Thickness of tissue increases, scatter increases.
Lower density tissue scatters more bad absorbs less.
As KVP increases, scatter production increases.
Collimator
A primary tool used to minimize the production of scatter
Grid
A primary tool used to minimize the impact of scatter
Remnant radiation
Primary X-ray that passes through the patient
Photon/Quanta/Ray
The smallest quantity of any type of electromagnetic energy, a small bundle of energy.
Electromagnetic energy
Energy in transit through space, bundles of pure energy, no mass, no charge, speed of light, waveform movement
Common properties to all forms of EMR
Bundles of pure energy, no mass, no charge, speed of light (c), waveform movement
Frequency
The number of wavelengths that pass a given point per second
Measured in hertz (Hz)
Wavelength
The distance from one crest to the next, or valley to valley
Measured in meters
Represented by the Greek letter lambda
Amplitude
One half the range from crest to valley
Speed of light
Constant, velocity
186,400 miles per second or
3x10 to the 8th meters per second
Wave equation
Speed of light = frequency x wavelength
Ionizing radiation
Energy with the ability to disrupt atomic structure thereby ionizing meter.
2 types: 1)energy based, 2)matter based
Properties of energy based ionizing radiation:
Waves
Pure energy, no mass, no charge, speed of light, waveform movement
Properties of matter based ionizing radiation
Particles.
Have matter, have mass, can have charge, slower than the speed of light, straight line movement
Wave particle duality
The ability to ionize matter by disrupting normal atomic structure.
Both energy based and matter based possess this ability.
Linear Energy Transfer - LET
Energy deposited in tissue per unit of difference
Quality factor / Wr
Adjustment multiplier used in the calculation of dose equivalence to specify the ability of a dose of any kind of ionizing radiation to cause biological damage
The quality factor of X-ray is
1 (one)
The quality factor of gamma is
1 (one)
Quality factor of alpha is
20 (twenty)
Compton interaction
Primary X-ray enters atom and collides with outer shell electron (low electron bind). X-ray easily overcomes the binding energy and electron ejected, the atom is ionized in the process. Incoming X-ray loses energy in collision, the energy is spent ejecting the outer shell electron. Incoming X-ray is redirected or scattered due to the collision.
Classical/Coherent/Thompson/Rayleigh Interraction
Low energy photon approaches atom, energy absorbed by entire atom. Atom cannot hold excess energy, releases new (secondary) photon. Energy is exactly same as primary X-ray and proceeds isotropically.
Photoelectric interaction
High energy X-rays collide with inner shell electron, primary X-ray dies in collision, it’s energy is transferred. Hole left in K shell causing characteristic cascade. The strength of the X-ray created us exactly equal to the difference in orbital ring change. X-ray too weak to exit patients body and absorbed.
Nuclear accidents
Radioactive debris from power plant accidents
Amplitude
One half the range from crest to valley
Velocity
For all electromagnetic radiation it is constant at the speed of light.
EMR interacts with
Objects whose size approximates its own wavelength
As frequency increases
Wavelength decreases
Ionizing radiation includes
X-radiation and gamma radiation - possess enough energy to ionize matter.
The only difference between x-radiation and gamma radiation
X-rays are emitted from the electron shells of an atom
&
Gamma radiation is emitted from the nucleus of a radioactive atom.
If given an X-ray and gamma ray with equal energies
You would not be able to tell them apart
As frequency increases
Wavelength decreases
As frequency decreases
Wavelength increases
As wavelength decreases
Energy increases
As frequency increases
Energy increases
High energy EMR like X-ray possesses
Short wavelength and high frequency
RBE - relative biologic effectiveness
Biologic reaction compared to a standard
OER - Oxygen Enhancement Ratio
Oxygen deprived versus oxygen rich environment
When X-ray enters a patient:
X-ray energy passes through without Interraction
Xray energy is absorbed in patient due to interraction
X-ray energy is redirected due to interaction (scatter)
Scatter
Redirected primary beam radiation caused primarily by Compton interactions within tissue.
As wavelength decreases
Energy increases
As frequency increases
Energy increases
High energy EMR like X-ray possesses
Short wavelength and high frequency
The X-ray beam is polyenergetic
Waveform, and energy values, will vary within the polyenergetic beam up to the peak energy - KVP.
Low energy X-rays
1-30 KVP range
Relatively long wavelength (entire atoms)
Moderate energy X-rays
30-50 KV range
Moderate wavelength (outer shell e- orbits)
High energy X-rays
50+ KV range
Relatively shoer wavelength (inner shell e- orbits)
