Chapter 3 Flashcards
If x-rays enter a material, they may:
- interact with the atoms of the patient
- pass through without interaction
Energy transferred from the x-rays to the atoms of the patient’s biologic material
Absoprtion
The amount of energy absorbed per unit mass
Absorbed dose
A diagnostic x-ray beam is produced when a steam of high-speed _________ bombards a ___________ charged target in a highly evacuated glass tube
Electrons
Positively
What is the anode made up of
Tungsten (metal)
Rhenium (alloy metal)
Reasons tungsten and rhenium are used as target materials
High melting points
High atomic numbers
Built-in filtration
Inherent
A certain thickness of added aluminum to harden the beam
Added filtration
Removes low-energy x-ray photons
Total filtration
What makes up the permanent inherent filtration in the xray tube
Glass window and added aluminium
X-ray photon beam that emerges from the x-ray tube and is directed toward the image receptor
Primary radiation
The most energetic photons in the beam can have no more energy than the:
Electrons that hit the target
The energy of the electrons inside the xray tube is expressed in terms of
Electric voltage
In diagnostic radiology the energy of the electrons is expressed in
Volts or kV
If an electron is drawn across an electric potential of 1 volt, it has acquired energy of:
1 eV
100 kVp means that the electrons bombarding the target have a maxium energy of _____ eV
100,000 eV
X-rays of various energies are produced, but the most energetic x-ray photons can have no more energy than:
100 keV
The energy of the average photon is ___ of the energy of the most energetic photon
1/3
Some primary photons will traverse the patient without interacting
Direct transmission
Other primary photons can undergo _______ or _______ interactions and as a result may be scattered or deflected.
Compton or Coherent
Type of transmission where photons that interact with the patient but still strike the IR
Indirect transmission
Optimal x-ray image is formed only when ______ xray photons hit the IR
Direct transmission
Small-angle scatter events cause this effect on the IR
Fog
What is one way to reduce fog?
Collimate
How many types of x-radiation and matter are possible
5
Only __ out of 5 interactions between x-radiation and matter are important in diagnostic radiology
2/5
A simple process that results in no loss of energy as x-rays scatter
Coherent scattering
When does Coherent scattering occur
Low-energy photons, less than 10 keV
Because the wavelengths of both _______ and ______ waves are the same, no net energy has been absobred
Incident
Scattered
How does Rayleigh and Thompson scattering effect radiography
It doesn’t
Other names for Coherent scattering
Classical
Elastic
Unmodified
What kVp does photoelectic absorption occur?
23-150 kVp
What type of scatter is the most important mode of interaction between xray photons and the atoms of the patient’s body for producing useful images
Photoelectric
What type of interactions causes the Auger effect
Photoelectric
Who discovered the Auger effect and when
Pierre Victor Auger
1925
Photoelectric absorption increases as the energy of the photon:
Decreases
Photoelectric absorption increases as the atomic number of the irradiated atom:
Increases
The less a give structure attenuates radiation, the ______ will be its radiographic density on a film
Greater
The more a given structure attenuates, the _______ will be its radiographic density on a film
Lesser
When radiographic film is no longer used as the primary IR, the term _________ is used in the digital environment
IR exposure
A monitor function that can change the lightness and darkness of the image on a display monitor
Brightness
Sets the midpoint of the range of densities visible on the image
Window Level
The greater the difference in the amount of photoelectric absorption, the _________ the contrast in the image will be
Greater
As absorption increases, so does the potential for:
Biological damage
To ensure both radiographic image quality and patient safety, choose the _____ energy x-ray beam that permits adquate contrast
Highest
Additional names for Compton scattering
Incoherent
Inelastic
Modified
An interation that occurs at more than 10 MeV in high-energy radiation therapy treatment machines
Photodisintegration
Type of photons that have undergone either absorption or scatter
Attenuated
Type of photons that give up all of their energy and cease to exist
Absorbed
Type of photons that interact with atoms but only surrender part of their energy
Scattered
A composite Z value by weight for a material that is composed of multiple chemical elements
Effective Atomic Number
Measured in grams per cubic cm
Mass density
What causes small angle scatter
When the photon interacts with the patient, it causes a bend it the photon’s path
Tungsten atomic number
74
Rhenium atomic number
75
Filtered x-ray photon beam is known as
Primary radiation
What does kV measure
Voltage on the xray tube
What does keV meausre
Energy of specific xrays
Number of x-rays emitted per inner-shell vacancy
Fluorescent yield
Barium atomic number
56
Iodine atomic number
53
What type of scatter is not dependent on the atomic #
Compton
Pair production occurs when x-ray photon energy is:
1.022 MeV
Examples of unstable nuclei used in PET scanning
Fluorine
Carbon
Nitrogen
What happens during a photodisintegration event
High energy photon is absorbed by nucleus of an atom
Atom emits neutrons to regain stability
