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60 Cards in this Set
- Front
- Back
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What are the two sources of radiation? |
1. Man-made 2. Natural |
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What is the difference between Gamma Rays and X-rays? |
Gamma Rays are given off by interactions in the nucleus and X-rays interact with photons from the shells |
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What are the two types of ionizing radiation? |
Electromagnetic radiation and Particulate |
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What are the three main parts of the x-ray imaging system? |
1. Operating Console 2. High Voltage Generator 3. X-ray Tube |
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When were x-rays discovered? |
November, 1895 |
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How were x-ray discovered? |
Roetgen was playing with his Crooke's tube and accidentally discovered them. |
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What year was the Coolidge tube invented? |
1913 |
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What is Thermionic Emission? |
Electrons are heated up and boiled off of the filament |
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What is Space Charge? |
The boiled off electrons form a cloud around the filament |
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What is the purpose of the focusing cup? |
The focusing cup repels the electrons because the focusing cup is negative just like the electrons. Because it repels them, the electrons are able to be send to the cathode in a direct stream. |
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Name the layers of the cathode and what they're comprised of |
Outer Layer: Tungsten Middle Layer: Molybdenum Inner layer: Graphite |
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Why use Tungsten? |
High melting point and high atomic number(more energy photons) |
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What is the melting point of Tungsten? |
3370 celsius |
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What is Saturation Current? |
The max amount of current that can be applied to the filament. Once that max is reached, no more electrons are able to get boiled off. |
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What is the focusing cup made out of? |
Nickel |
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How does the rotor on the anode spin? |
There are stators located on the outside of the x-ray tube. using magnets and mutual induction, the rotor spins. |
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Explain Bremsstrahlung Interactions |
Incident electrons interact with the force field of the nucleus. The electron is stopped by the nucleus and the energy that is lost while it is stopping is given off as an x-ray photon. |
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Explain Characteristic Radiation |
Incident electrons interact with inner shell electrons. The electron will knock an inner shell electron out and it will be given off as a photon. An electron from another shell must drop in to fill the gap from the inner shell electron that was knocked out. |
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What is Characteristic Cascade? |
Happens when an electron is released from the K-shell. An L-shell electron must drop in to fill the hole. Then, an M-shell electrons drops in to fill the hole in the L-shell. All these movements result in different energy photons being given off. |
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What four things are needed to produce an X-ray? |
1. Source of electrons 2. Voltage to drive them 3. A way to stop them 4. Vacuum |
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What is density? |
The blackness of an object |
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What is contrast? |
The differences in the blackness |
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What is Isotropic Emission |
X-rays hit the target and fly off in many different directions- creates a spherical pattern. |
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What three things affect your amplitude on the Emission Spectrum? |
mAs, kVp, and what rectification you're using |
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What is the line focus principle? |
By angling your target more, you increase your actual focal spot size and decrease your effective focal spot size |
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What is the target angled at to get the smallest possible effective focal spot? |
12 degrees |
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What is the anode heel effect? |
Electrons from the target travel back toward the cathode side resulting in a higher intensity beam on the side of the cathode. |
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Properties of X-rays |
1. travel in a straight line 2. invisible 3. travel at the speed of light 4. many different energies 5. can produce scatter radiation 6. can cause biological damage 7. highly penetrating 8. cause materials to glow 9. affect radiographic film |
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What is Scatter Radiation? |
Produced when x-rays enter a patients body. Some can get absorbed and some can fly off in different directions |
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What is Secondary Radiation? |
photons are given off in your body when electrons interact with other atoms. |
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Any radiation that exits the window is called |
Useful Beam |
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Radiation that does not hit the target is known as? |
Off-Focus Radiation |
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Why do tubes fail? |
1. Not warming up the tube 2. Tube arcing 3. Filaments can break |
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What is the purpose of the protective housing? |
Catches leakage radiation, absorbs heat, mechanical support, insulates |
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What does the tube rating chart tell you? |
You are able to figure out if the limits of your exposure are safe or not |
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Heat Unit constants |
Single phase: 1.00 3 phase, 6 pulse: 1.35 3 phase, 12 pulse: 1.41 High frequency: 1.45 |
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Heat Unit Equation |
HU= mAs x kVp x HU Constant |
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What is filtration? |
process of eliminating low-energy photons by insertion of absorbing materials |
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What is inherent filtration? |
Any type of filtration found within the x-ray tube - glass or metal enclosure - dielectric oil - window |
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What is the mm of aluminum equivalent for inherent filtration? |
.5 mm Al/Eq |
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What is Added Filtration? |
Any filtration found outside the tube. - collimator |
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How many sets of shutters are on the collimator? |
1. Top set: gets rid of the low-energy photons 2. Bottom Set: shapes the beam |
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What is the mm Aluminum equivalent for added filtration? |
2 mm Al/Eq |
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What is Total Filtration? |
Inherent filtration plus added filtration |
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What is the minimum total filtration level? |
2.5 mm Al/Eq |
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Who decides what the minimum total filtration level is for a diagnostic x-ray room? |
NCRP |
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What is the Half Value Layer? |
The amount of absorbing material it takes to reduce the beam intensity to 1/2 its original value. |
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What is compensatory filtration? |
filters that are added to compensate for part thickness and differences in radiopacity. Makes the beam more uniform throughout |
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Quantity and intensity of the beam is affected by the |
mAs |
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Quality of the beam is affected by |
kVp |
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Factors affecting the quantity of the x-ray beam |
distance, mAs, kVp, filtration |
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Factors affecting the quality of the beam |
kVp and filtration |
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What is the 15% Rule? |
If you increase your kVp by 15%, you must cut your mAs in half. |
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What are the two scales on contrast? |
1. Long scale- low contrast- more gray 2. Short Scale- high contrast- more black/white |
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What happens to your contrast as your kVp increases |
Contrast decreases |
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As your distance increases, what happens to your beam intensity |
Your beam intensity decreases as your distance increases |
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What is Coherent Scattering? |
Happens when low energy photons interact with the atoms and cause the electrons to vibrate and become unstable. Once they calm back down, they give off photons |
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What is photoelectric Absorption? |
The x-ray photon knocks an electron out of the K-shell and gets absorbed. The ejected k-shell electron is now called a photoelectron which gets absorbed in the soft tissue. An outer shell electron then must fill the empty K-shell which releases a characteristic photon. |
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For photoelectric Absorption to occur.. |
The energy of the photon must be more than the binding energy of the electrons |
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What is Compton Scatter? |
Incoming photon knocks an electron from its shell and distributes half of its energy to it. The electron is now called a recoil electron. The incoming photon now goes off in a different direction with less energy. If it goes back to the source is it called backscatter. |
