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RAD121
Chapter 7 Study Questions
| Question | Answer |
|---|---|
| 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-. |
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queenxraynay
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