Ch. 7 X-ray production Flashcards
Kinetic energy is…
energy in motion
Objects in motion have kinetic energy proportional to their…
mass and to the square of their velocity
KE =
1/2 mv^2 (m= mass; v = velocity)
all electrons have the same…
mass
In an xray tube the projectile is the…
electron
electron kinetic energy is increased how?
by raising the kVp
When electron kinetic energy is increased what happens/
both the intensity (quantity) and energy (quality) of the xray beam are increased
What is the distance of the filament to the xray tube target?
about 1 cm
How fast are the electrons moving from the time it leaves the filament to the time it hits the target?
almost half the speed of light
What are projectile electrons?
electrons traveling from cathode to anode
What happens when projectile electrons hit the heavy metal atoms of the xray tube target?
They transfer their kinetic energy to the target atoms
What do the projectile electrons interact with?
orbital electrons or the nuclear field of target atoms.
What is the result of the interactions between the projectile electrons and orbital electrons?
a conversion of electron kinetic energy into thermal energy (heat) and electromagnetic energy in the form of infrared radiation and xrays.
How much of the projectile electron kinetic energy is used for the production of xrays?
only 1%
doubling the xray tube current doubles what?
it doubles the heat produced
Heat production increases directly with…
increasing kVp
The efficiency of xray production increases with…
increasing kVp
When are characteristic xrays produced?
When a projectile electron interacts with an inner shell electron of the target atom rather than with an outer shell electron.
When the interaction is sufficiently violent to ionize the target atom through total removal of an inner shell electron what happens?
characteristic xrays
Characteristic xrays are emitted when an ____ electron fills and _____ void.
outer shell; inner shell
The transition of an orbital electron from an outer shell to an inner shell is accompanied by…
the emission of an xray
The energy of an xray is equal to…
the difference in the binding energies of the orbital electrons involved.
The energy from M-K, N-K, O-K, and P-K can be…
calculated
When are characteristic x-rays produced?
when the target atom is ionized by removal of electrons from shells other than the K shell.
Only the K-characteristic x-rays of ____ are useful for imaging.
tungsten
Characteristic x-rays can only be produced at specific…
energies equal to the differences in electron-binding energies for the various electron transitions.
Why is characteristic x-ray production called characteristic?
Because it is characteristic of the target element.
The effective energy of characteristic x-rays increases with…
increasing atomic number of the target element.
The production of hea and characteristic x-rays involves interactions between…
the projectile and the electrons of x-ray tube target atoms.
Describe a bremsstrahlung interaction.
Bremsstrahlung x-rays are produced when a projectile electron is slowed by the nuclear field of a target atom nucleus.
What does the word bremsstrahlung mean?
it is a german word meaning slowed down radiation
Bremsstrahlung x-rays can be considered radiation that results from…
the braking of projectile electrons by the nucleus.
A projectile electron can lose any amount of its kinetic energy in an interaction with the nucleus of a target atom and the bremsstrahlung x-ray associated with the loss can take on what?
the corresponding values
How does a low energy brems x-ray result?
When the projectile electron is barely influenced by the nucleus.
How does a high energy brems x-ray result?
when the projectile electron loses all its kinetic energy and simply drifts away from the nucleus.
What kind of brems x-rays are most frequent?
The ones between low and highest energy.
In diagnostic range, which type of x-rays are the most common?
brems
What does the energy of the electron have to be in order to create at brems x-ray?
it can be at any energy
A discrete spectrum contains….and a continuous spectrum contains….
only specific values….all possible values
What kind of x-ray spectrum do characteristic x-rays have?
the energies of characteristic x-rays are fixed so the emission spectrum would be discrete
The Brem x-ray emission spectrum extends from ___ to ____
0 to maximum projectile electron energy
The highest number of brem x-rays only have about ____ of the maximum energy of the beam.
1/3
Brem x-rays have a ___ of energies and form a _____ emission spectrum.
range; continuous
With brems, the number of x-rays emitted ____ at very low energies.
decreases
The energy of an x-ray is equal to..
the product of its frequency and Planck’s constant
x-ray energy is inversely proportional to what?
its wavelength
As x-ray wavelength increases, x-ray energy….
decreases
If the curve of an emission spectrum goes to the right what does that indicate?
he higher the effective energy or QUALITY of the x-ray beam
The larger the area under the curve of an emission spectrum indicates…
higher x-ray intensity or QUANTITY
A change in mA or mAs results in what kind of change in the emission spectrum?
a change in the amplitude but not the position
As kVp is raised, how does the emission spectrum change? (factor)
the area under the curve increases to an area approximating the square of the factor by which kVp was increased.
When kVp changes, how does the appearance of the spectrum change?
in amplitude and position
What is the % of change in kVp that needs to happen to be equal to doubling mAs?
15%….15/50 rule
What affect does adding filtration have on the beam?
It reduces intensity while increasing the average energy.
What is a word used when adding filtration to a beam?
hardening
Does the atomic number of the target affect the quantity and quality of the beam? How?
yes as the atomic number of the target material increases, the efficiency of the production of bremsstrahlung radiation increases, and high energy x-rays increases in number to a greater extent than low energy x-rays.
What are the 5 voltage waveforms?
half wave rectified, full wave rectified, 3 phase/6 pulse, 3 phase/12 pulse, and high frequency
What is the relationship between full wave and half wave rectified?
They are the same except for the frequency of x-ray pulse repetition.
What is the relationship between 3 phase/6 pulse and 3 phase/12 pulse?
There is reduced ripple with 12 pulse generation compared with 6 pulse generation
What produce the lowest voltage ripple of all high voltage generators?
high-frequency generators
Because of reduced ripple, operation with 3 phase power or high frequency is equivalent to ….
about 12% increase in kVp, or almost a doubling of mAs over single phase power.
