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RAD121

Chapter 7 Study Questions

QuestionAnswer
The approximate percentage of electron kinetic energy that is converted to x-ray photon energy in the x-ray tube is... 1%
The majority of the electron kinetic energy in the x-ray tube is converted to what form of energy? Heat,thermal,or infrared
Describe a bremsstrahlung target interaction. An incident electron reacts with the force field of the nucleus, causing the electron to slow down, diverting the electron’s course; the electron loses energy and changes direction; the energy lost in the "braking" is a bremsstrahlung photon.
Describe a characteristic target interaction. An incident electron interacts with an inner shell electron, knocking out the inner shell electron and continuing in a slightly different direction, which creates a hole in the inner shell, making the shell unstable.
What is a characteristic cascade? The reaction of electrons dropping into the holes created during a characteristic interaction until there is only a hole in the outer shell.
What is the average keV of the primary beam as compared to the kVp? The average primary beam photon has a keV energy of only about 30-40 percent of the kVp.
What effect does changing mAs have on the total x-ray emissions spectrum? When mAs is changed the result is a change in the amplitude of the emission graph.
What effect does changing kVp have on the total x-ray emission spectrum? When kVp is changed, the result is a change the # of higher-energy photons, as well as in the amplitude of the emission graph.
Characteristic Peak Occurs when K-shell emissions reach their effective energy range of 69 keV
Incident Electrons The electrons from the thermionic cloud that arrive at the anode target.
Target Interaction The actions that take place when the electrons strike their target or focal spot.
How are x-ray photons produced? When the high-speed electrons from the cathode strike and anode target in an x-ray tube.
How do x-rays and gamma rays differ in their production? x-rays are man made; gamma rays are products of nuclear radioactive decay.
At what speed are the e- traveling when they reach the anode target? Almost the speed of light.
How far is the anode from the cathode? 2 cm
What is the symbol for incident e- in a drawing? solid arrow
What is the symbol for a photon in a drawing? wave arrow
What is the quality also refered to as? energy
Kinetic Energy The energy of motion.
Excitation Process in which e- in an atom are moved to a higher energy state without actually being removed from the atom; produces heat
Ionization the process of adding or removing an e- from an atom
What are other some names for incident electrons? projectile or incoming electrons
What is infrared radiation? heat
Where do all target interactions occur? Within .25 to .5 mm of the target surface.
What are the 3 possible products of target interaction? --1.heat--2.Brems Interactions--3.Characteristic Interactions
What does mA control? The quantity of e- available at the cathode.
What does kVp control? The quality (energy) of e- ~~~which, in turn, controls the number and quality of photons (high-energy;penetrating)~~~
Why is tungsten a good target material for x-ray production? --1.high Z#--2.high melting point--3.similar e- binding energies
Bremsstrahlung is German for what? braking
Within the diagnostic x-ray range, most photons are produced by what? Brems target interactions
In characteristic interactions, the e- must drop where for a photon to be produced within the diagnostic range? the K-shell
How many interactions do electrons undergo before dissipating excess energy? 1000+
What is intensity also referred to as? quantity
How would you increase e- kinetic energy? increase kVp
When e- kinetic energy is increased, what 2 things are also increased? intensity and energy of the x-ray beam
What is the imaging system designed to do? to provide a large number of e- with high kinetic energy focused to a small spot on the anode
The e- traveling from the cathode to the anode constitute what? the x-ray tube current
When projectile e- hit the x-ray tube target, the transfer what to the target atoms? kinetic energy
What might a projectile e- interact with? an orbital e- or the nuclear field of a target atom
What is the definition Mrs. B wants us to know for Brems radiation? X-rays produced when a projectioe e- is slowed and its direction is changed by the electric field of a target atom
When is a characteristic x-ray emitted? when an outer-shell e- fills an inner-shell void
Only the K-characteristic x-rays of which element are useful in imaging? tungsten
Characteristic photons will not compose any of the useful beam until kVp is what? Why? > or = 70; removal of a K-shell e- requires 69.5 keV
What type of spectrum contains only specific values? discrete
What type of spectrum contains all possible values with the photons ranging from zero to some maximum value? continuous
Precisely fixed energies are representative of what type of photon? Characteristic x-rays
All ranges of energies are representative of what type of photon? Bremsstrahlung x-rays
The area under the curve of the x-ray emission spectrum is equivalent to what? amplitude (total # of x-rays emitted)
The farther to the right a spectrum is.... the higher the effective energy or quality of the x-ray beam.
Between 80 and 100 kVp you can expect the primary beam to be produced by what types and percentages of x-rays? 80-90% brems and 10-20% characteristic.
What is the minimum kVp for characteristic x-ray production in the diagnostic range? 70
At < 70kVp you can expect what type of target interaction? brems
A decrease in voltage ripple will produce what on the emission spectrum? --1.higher amplitude--2.increased #of photons--3.increase in high energy photons
What are the 2 target interactions that can produce x-rays? brems and characteristic.
What determines the energy of a photon created in a brems interaction? The exact difference between the entering and exiting kinetic energy of the e-.
How do you determine the energy of a characteristic x-ray? It is exactly the difference of the binding energies of the outer and inner shells between which the e- dropped.
What does "all or nothing" refer to? a direct brems interaction with the nucleus; maximum energy photon
As the electron gets closer to the nucleus in brems, what occurs? --1.photon energy increases--2.larger deflection of the incident e-.
Created by: queenxraynay on 2008-07-29



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