Rad 260: Safety Flashcards
Radiation Safety
Ionizing radiation
radiation that possesses the ability to remove electrons from atoms by a process called ionization
Somatic effects
effects of radiation on the body being irradiated
Genetic effects
effects of radiation on the genetic code of a cell; affects the next generation
National Academy of Sciences/National Research Council Committee on the Biological Effects of Ionizing Radiation (NAS/NRC-BEIR)
organization that studies biological effects of ionizing radiation and publishes resulting data
National Council on Radiation Protection and Measurements (NCRP)
organization that publishes radiation protection guidelines for the United States
Nuclear Regulatory Commission (NRC)
organization that enforces radiation protection standards at the federal level related to use of radioactive material
Effective dose limit
upper boundary dose that can be absorbed, either in a single exposure or annually, with a negligible risk of somatic or genetic damage to the individual; effective dose implies whole-body radiation exposure
As low as reasonably achievable (ALARA)
concept of radiologic practice that encourages radiation users to adopt measures that keep the dose to the patient and themselves at minimal levels
Direct effect
effect that occurs when radiation directly strikes DNA in the cellular nucleus
Indirect effect
effect that occurs when radiation strikes the water molecules in the cytoplasm of the cell
General types of radiation damage
somatic and genetic
Primary radiation
Radiation exiting the x-ray tube
Exit radiation (image-producing radiation)
X-rays that emerge from the patient and strike the image receptor; composed of primary and scattered photons
Attenuation
Absorption and scatter (loss of intensity) of the x-ray beam as it passes through the patient
Heterogeneous beam
X-ray beam that contains photons of many different energies
What are the most common photon–tissue interactions in diagnostic radiography?
Photoelectric and Compton interactions
Photoelectric interaction
a.Photon absorption interaction
b.Incoming x-ray photon strikes a K-shell electron
c.Energy of x-ray photon is transferred to electron
d.Electron is ejected from the K-shell and is now called a photoelectron
e.X-ray photon has deposited all of its energy and ceases to exist
f.Photon has been completely absorbed
g.Photoelectron may ionize or excite other atoms until it has deposited all of its energy
h.Hole in K-shell is filled by electrons from outer shells, releasing energy that creates low-energy characteristic photons that are locally absorbed
i.Photoelectric interaction results in increased dose to the patient
j.Photoelectric interaction produces contrast in the radiograph because of the differential absorption of the incoming x-ray photons in the tissues
Compton interaction
a.Also called Compton scattering or modified scattering
b.Incoming x-ray photon strikes a loosely bound, outer-shell electron
c.Photon transfers part of its energy to the electron
d.Electron is removed from orbit as a scattered electron, referred to as a recoil electron
e.Ejected electrons may ionize other atoms or recombine with an ion needing an electron
f.Photon scatters in another direction with less energy than before because of its encounter with the electron
g.Scattered photon may interact with other electrons, causing more ionization, additional scattering events, or photoelectric absorption; or it may exit the patient
h.Scattered photons emerging from the patient travel in divergent paths in random directions
i.Scattered photons may also be present in the room and expose the radiographer or radiologist
Coherent scatter (also known as classical scatter)
a.Produced by low-energy x-ray photons
b.Atomic electrons are not removed but vibrate because of the deposition of energy from the photon
c.As the electrons vibrate, they emit energy equal to that of the original photon
d.This energy travels in a path slightly different from the path of the original photon
e.Ionization has not occurred, although the photon has scattered
f.Does not affect image less than 70 kVp
g.May have negligible effect on fog greater than 70 kVp
Pair production
a.Does not occur in radiography
b.Produced at photon energies greater than 1.02 million electron volts
c.Involves an interaction between the incoming photon and the atomic nucleus
Attenuation
describes changes in the intensity of the x-ray beam as it traverses the patient
Which interaction results in complete absorption of an incoming x-ray photon?
Photoelectric interaction results in complete absorption of an incoming x-ray photon; this interaction produces contrast in the radiographic image
Which interaction results in scattering of the incoming x-ray photon?
Compton interaction results in scattering of the incoming x-ray photon; scatter produced by this interaction must be removed from the beam before it strikes the image receptor
What is the source of exposure to the radiographer or radiologist during fluoroscopy?
Compton scatter
