Ch. 6 X-ray Production
Binding energy of the K shell (tungsten)
69.5 keV
A tungsten atom has ____ orbiting its nucleus in six different shells.
74 electrons
continuous emission spectrum
a graphic representation of bremsstrahlung x-ray production
discrete emission spectrum
a graphic representation of characteristic x-ray production
Absorption also depends on the ______ of body tissues through which the x-ray photons are passing.
density
Characteristic photons have _______
discrete emission spectrum
A 15% increase in kVp is equivalent to _____ the mAs
doubling
In order to remove the orbital electron, the filament electron must have kinetic energy _______ than or equal to the binding energy of the electron with which it interacts.
greater
Beam quality is measured by the ______
half-value layer (HVL)
bremsstrahlung
the filament electron misses all of the orbital electrons & interacts with the NUCLEUS of the target atom.
Ionizing
the removal of an electron ONLY in characteristics
Kinetic Energy
the result of producing x-ray (photons)
Half Value Layer (HVL)
the thickness of absorbing material (aluminum or aluminum equivalent filtration) necessary to reduce the energy of the x-ray beam to one-half its original intensity
half-value layer is defined as
the thickness of absorbing material necessary to reduce the energy of the beam to one-half its original intensity
Primary Beam
the x-ray beam as it is upon exiting the collimator & exposing the patient
Remnant Beam
the x-ray beam that remains after interaction with the patient & is exiting the patient to expose the image receptor
primary beam
the x-ray beam upon exiting the collimator and exposing the patient
Changes in generator type change...
the x-ray production efficiency of the machine
Can any outer shell electron fill an inner shell vacancy?
Yes, it is not very likely to happen bc of the far distance.
The filament electrons penetrate the face of the target to a depth of approximately
0.5mm
Each filament electron may undergo ______ or more interactions before coming to rest.
1,000
Normal HVL of general diagnostic beams is
3 to 5 mm Al
If 90 kVp is selected at the control panel, then we can predict that the average energy of that beam is ______
30 kVp
x-ray emission spectrum
A graphic representation of the x-ray beam as a whole, *combining* the relevant parts of the discrete and continuous emission spectra.
In beam quantity an increase in: Filtration
Affect on Quantity: Decreases
In beam quantity an increase in: Distance
Affect on Quantity:Decreases
Breamsstrahlung (brems) Interactions
An interaction in which a filament electron is attracted to the nucleus, causing it slow down and change direction. The energy loss is emitted as a bremsstrahlung photon.
electron volts
Binding energy is measured in
In this type of interaction, the filament electron misses all of the orbital electrons of the target atom and interacts with the nucleus.
Bremsstahlung
The kinetic energy it loses in this process is emitted as an x-ray photon called a ______ or ______ photon.
Bremsstrahlung; brems
In beam quantity an increase in kVp
Effect on Quantity: Increases
In beam quantity an increase in mAs
Effect on Quantity: increases
Beam quality is affected by _____ and mainly ______
Filtration and kVp
In a tungsten target used for diagnostic imaging, most of the photons will be bremsstrahlung for two reasons.
First, with characteristic interactions, only those involving the K shell are of sufficient energy to be useful Second, the filament electron is more likely to miss the K shell electrons of the target atom than it is to hit it because the atom is mostly empty space.
High energy x-ray beams (high kVp) are called
High quality or hard
True
Most of our x-rays are produced are through Bremmsstrahlung
binding energy
The energy that holds protons and neutrons together in the nucleus through the force of attraction; the amount of energy needed to break up the nucleus.
inverse square law
The intensity of a source of radiation is inversely proportional to the square of the distance.
beam quality
The penetrating power of the x-ray beam
penetration
The process by which x-ray photons are transmitted through the body and reach the radiographic film.
Characteristic Cascade
The process of outer-shell electrons filling inner-shell vacancies, creating a cascading effect during a characteristic interaction.
transmitted
The state of light, or x-ray photons, that have passed through a substance such as air, clear glass, or different substances in the patient's body.
Inherent Filtration (0.5 mm Al) and Added Filtration (2.5 mm Al)
The total filtration is equal to the sum of?
beam quantity
The total number of x-ray photons in a beam
remnant beam
The x-ray beam that remains after interaction with the patient and is exiting the patient to expose the image receptor
Why is it that medical imaging generally focuses on K-shell interactions?
They are the highest energy and the most useful for imaging purposes
- Characteristics Interactions - Bremmsstahlung Interactions
What are the two types of x-ray production?
Changes in mA...
affect beam quantity
Changes in kVp....
affect quality & quantity
What type of material are filters made of?
aluminum or aluminum equivalent.
Characteristic Interaction
an interaction in which a filament electron removes and orbital electron from an atom, to regain stability, an outer-shell electron fills the vacancy, giving up its excess energy as a characteristic x-ray photon
A graph of brems photons creates a ______
bell- shaped continuum
Characteristic photons are so named because their energy is "characteristic" or dependent on the difference in______ between the shells involved.
binding energy
Bremsstrahlung is a German word for______
braking or slowing down.
Photons
bundles of energy
This process of outer shell electrons filling inner shell vacancies continues down the line, creating a ______
cascading effect
There are two ways in which these interactions occur:
characteristic and bremsstrahlung (brems)
This energy is given off as a ______
characteristic photon
Added Filtration
comes in the form of another 2.0 mm Al placed between the target window and the top of the collimator
Brem photons have a ______
continuous emission spectrum
What graphically illustrates the x-ray beam
emission spectrum
The removal of the orbital electron established the _____ for the x-ray production, and it is the expending of energy during the cascade the produces characteristic x-rays.
environment
In order to regain stability, the void created by the interaction with the _______ electron must be filled
filament
In a characteristic interaction, the ________ enters a target atom and strikes one of the orbital electrons, removing it from its orbit and the atom (if it has enough kinetic energy).
filament electron
The strength of the attraction depends on ______
how close the filament electron passes to the nucleus
As kVp increases, the beam's ability to penetrate matter _____
increases
Inherent Filtration
inherent to the tube head assembly, the target window (0.5mm Al) is the primary contributor
If a filament electron has kinetic energy equal to 50 keV and it hits a K shell electron of a tungsten atom, does it have enough energy to remove the electron?
it does not have the energy to remove the electron because the K shell electron binding energy is 69.5 keV
The characteristic photon is named for the shell being filled
k shell= k characteristic photon l shell= l characteristic photon etc.
High-energy photons result from higher ______
kVp settings.
Low energy x-ray beams (low kVp) are called
low quality or soft
5 factors change the appearance of the x-ray emission spectrum:
mA,kVp, tube filtration, generator type, & target materialC
Beam Quantity is affected by:
mAs, kVp, distance& filtration
If a generator operates more efficiently
more filament electrons have the energy to produce x-rays, increasing quantity (amplitude of the curve)
The average energy of bremsstrahlung photons is _______ of the kVp selected at the control panel.
one-third
The peak of the curve is approximately ____ of the kVp indicated
one-third
An x-ray beam directed to a body can be described in terms of ______
penetration and absorption
The addition of tube filtration moves...
photons from the beam
To do this, an outer shell electron drops into the closer orbit. To occupy this closer orbit, the orbital electron must give up some of its _____
potential (stored) energy
Less dense structures with a much lower probability of absorption are said to be
radiolucent
Body structures that readily absorb x-rays are called
radiopaque
Beam Quantity
refers to the overall number of photons in the beam
Beam quality
refers to the penetrating power of the beam
Absorption
refers to those photons that are attenuated by the body and do not reach the image receptor.
What does brems attraction cause the filament electron to do?
slow down (brake) and change direction.
As the atomic number of the target material goes up
so does the average energy, quantity of photons, and the position of the discrete line of the spectrum
Beam quantity varies inversely as the ____ of the distance
square (inverse square law)
The closer the filament electron passes to the nucleus, the _____ the attraction
stronger
When the kVp is set too high for the body area being imaged...
the area will be overpenetrated and the image will be too dark overall
These photons do not pass through the body to expose the image receptor..
the areas of the body that absorb the most x-rays appear on the radiographic image as clear or white.
potential difference
the difference in electrical charge between two points in a circuit expressed in volts (the increased and decrease of positive attraction)
What is the purpose of added filtration?
to remove low- energy x-ray photons from the beam before they can expose the patient and contribute anything useful to the imaging process
High-energy photons are more likely to be ____ through the body rather than be absorbed in an interaction with atoms in the body.
transmitted
What is the remnant beam composed of?
transmitted photons and scattered photons
True or False: Most of the x-ray beam is made up of bremsstrahlung photons
true
True or False: The stronger this attraction, the more energy the filament electron loses and the stronger the resultant brems photon.
true
the vacancy created by this interaction causes the atom to be very ______
unstable
characteristic
when an electron in an inner SHELL is knocked from its orbit by a projectile electron.
Penetration
x-ray photons that are transmitted through the body and reach the IR
It is when the outer shell electrons release energy to fill this void that ______ are produced.
x-rays
