Chapter 8 Flashcards
X-ray photons are produced when the _________________ from the cathode strike an anode target.
High-speed electrons
What is the primary difference between x-rays and gamma rays?
That x-rays are human-made.
All target interactions occur within ____ - ____mm of the surface of the target.
0.25-0.5
What percentage of the kinetic energy is the incident electrons is converted to heat?
Over 99.8%
Why are modern x-ray tubes tremendously inefficient?
They waste over 99% of the energy they use
As the kinetic energy of the incident electrons increases, so does ____________________________.
The efficiency of photon production
What are the two types of target interactions that can produce diagnostic-range x-ray photons?
Bremsstrahlung interactions & characteristic interaction
What two things will occur to decide which interaction will take place?
Electron kinetic energy and the binding energy of the electron shells of the atom
What two metals are used as target materials?
Tungsten & rhenium
Why are tungsten and rhenium used as target materials?
As an effort to provide appropriate-atomic-number atoms and a maximum number of similar electron-shell binding energies.
How was bremsstrahlung interactions named?
By the German word for braking or slowing
When will berms interactions occur?
When the incident electron interacts with the force field is the nucleus
The incident electron must have enough _______ to pass through the orbital shells and approach the nucleus of the atom.
Energy
Why is there a mutual attraction between atomic nuclei and the incident electron?
Because atomic nuclei have a positive charge and the incident electron has a negative charge.
Why does the incident electron lose energy and change direction?
The force field is too powerful for the electron to penetrate. It causes it to slow down and diverts the electron.
How can you determine the amount of kinetic energy lost by the incident electron in a berms interaction?
The difference between the entering and exiting kinetic energy of the electron
What is the only way the electron would drift away to join the current flow in berms interaction?
When the incident electron loses all of its excess kinetic energy.
Can a single incident electron cause more than one brems interaction?
Yes, they can cause numerous interactions in many different atoms before losing enough energy to become included in the current flow.
A characteristic interaction can only occur when?
The incident electron interacts with an inner-shell electron.
The incident electron must have enough energy to do what in a characteristic interaction?
To knock an inner-shell electron from orbit
What happens to the atom when the incident electron knocks an inner-shell electron from orbit?
It ionizes the atoms
After the incident electron interacts in a characteristic interaction, does the incident electron continue on its original path or go on a different path?
It goes on a new path in a slightly different direction.
After the characteristic interaction the atom is considered _________, until an electron from another shell drops into the hole.
Unstable
What is the characteristic cascade?
When an outer-shell electron has dropped to fill the hole, another electron will drop to fill the hole it left so on until only the outer- most shell is missing an electron.
Is brems photons or characteristic photon energy so predictable?
Characteristic photon energy
Is brems photon energy or characteristic photon energy used by spectroscopy using the measurements of their photon energies to determine what types of atoms make up the sun, stars, and other celestial bodies?
Characteristic
What is the binding energy for the K-shell electrons?
69.5 keV
What is the binding energy for the L-shell electron?
12.1 keV
What is the binding energy for the M-shell electrons?
2.8 keV
What is the binding energy for the N-shell electrons?
0.6 keV
What is the binding energy for the O-shell electrons?
0.08 keV
How can characteristic photons be created?
From the incident electron ionization of any shell and hole filling from any shell.
A ____ variety of characteristics photon energy levels are produced.
wide
Most characteristic interactions will produce?
heat
Within the diagnostic x-ray range, mot photons are produced by __________ target interactions.
bremsstrahlung
Characteristic photons will not comprise any useful beam until the kVp is above what number?
70 because removal of a K-shell electron from tungsten requires 69.5 keV
Between 80 and 100 kVp, about __-__ percent of the primary beam is produced by brems interactions.
80-90
Between 80 and 100 kVp, about __ -__ percent of the primary beam is produced by characteristic interactions.
10-20
What two emissions combine to form the complete primary beam spectrum?
Brems and Characteristic
The kilovolatage peak of the exposure is the _______ possible energy for any photons that exits the x-ray tube.
maximum
kVp controls quality or quantity?
quality (energy)
mAs controls quality or quantity?
quantity
What is the x-ray emission spectrum affected by?
The quantity and composition of the materials through which it must pass to exit the x-ray tube and housing.
While the x-ray beam is passing through the filtering materials what is being abasorbed?
lower-energy photons
If filtration of the x-ray beam is increased, the image receptor exposure ______.
decreases; they are inverse
