Term
| Please list the 4 types of digitized imaging that still uses Ionizing Radiation |
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Definition
| - Computed Radiography, Direct Digital Radiography, CAT Scan and Nuclear Medicine (PET and Bone Scan) |
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Term
| 3 types of imaging that use Non-Ionizing Radiation |
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Definition
Non-ionizing
- MRI, Ultrasound and Thermography |
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Term
| 41. #3 What are the three Main Components of the X-ray Machine? |
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Definition
- The Tube- glass x-ray tube encased within a metal protective housing
- Control Console- operating console that controls the quantity and quality of x-rays produced
- Transformer Assembly- prepares the exact electrical output to the tube |
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Term
| 42. #5 What are the 4 things the Tube Housing does? |
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Definition
- Mechanical support for the glass x-ray tube,
-thermal cushioning,
-prevents radiation leakage
- prevents electrical shock. |
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Term
| 43. #7 What is “Leakage Radiation”? |
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Definition
| - Radiation that is emitted from any part of the housing other than the port window |
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Term
| 44. #7 What is the Guideline published by the NCRP to control Leakage Radiation? |
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Definition
| - Leakage radiation shall not exceed 100 mR/hour at 1m from the tube when the tube is operated at its maximum continuous radiated current for a maximal rated tube potential |
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Term
| 45. #16 What are the two parts of the Cathode of the tube? |
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Definition
- The filament-
- focusing cup |
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Term
| 46. #17 Please describe “Thermionic Emission” and where it is emitted from as given in the notes. |
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Definition
| - It is when there is enough heat to cause the outer shell electrons of the tungsten to release or boil off. It’s emitted from tungsten wire. |
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Term
| 47. #19 How many Filaments are usually in the tube? |
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Definition
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Term
| 48. #19 What is the relationship of the “boiling off” of the electrons and the “number “ of X-rays produced? |
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Definition
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Term
| 49. #20 What is the filament and what is it made from? |
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Definition
| - coil of wire made of tungsten… responsible for thermionic emission… supplied by the filament circuit. Also made from 1-2% thorium |
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Term
| 50. #22 What is the “Focusing Cup” regarding the filament and what does it do? |
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Definition
| - made of molybdenum and surrounds the filaments. Its negatively charged to condense the electrons stream. It is in charge of focusing the electron stream |
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Term
| 51. #3 Please explain “Line Focus Principle” regarding “effective focus spot as given in the notes. |
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Definition
| - As the target angle decreases, so does the effective focal spot size |
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Term
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Definition
| size of the area on the target that is being exposed to electrons from the catholde |
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Term
| 53. #9 What determines the actual focal spot size as given in the notes? |
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Definition
| - The size of the filament with the angle of the target remaining constant |
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Term
| 54. #10 & 11 What is the relationship to “penumbra” and Small focus: |
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Definition
| - Less penumbra but better detail (c-spine and extremities) |
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Term
| 55. #13 How does the focal spot size relate to the sharpness or unsharpness of recorded detail on the film Large focal spot: |
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Definition
| - Increases unsharpness causing a decrease in recorded detail |
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Term
| 56. #16-23 Please explain the “Anode Heel Effect” and its relation to the strength of the Primary Beam as given in the notes. |
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Definition
| - Results in uneven exposure, The lesser the anode angle the greater the heel effect. The intensity of the beam is greatest toward the cathode side. |
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Term
| 57. #20 When X-raying a body part that varies in thickness which part of the body thickness do you want the anode side of the tube pointed toward, as given in the notes? |
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Definition
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Term
| 58. #23 Under what circumstances is the Anode Heel Effect less noticeable, as given in the notes? |
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Definition
| - It is less noticeable with a larger focal spot to film distance (FFD). Due to collimation. |
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Term
| 59. #3 Please explain what “filters” do for the X-ray Beam as given in the notes. |
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Definition
| hardens the beam by increasing the average energy of the beam |
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Term
| 60. #5 Please explain the Federal law requirements of Beam Energy Filtration as given in the notes. |
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Definition
- Less than 50 kVp = 0.5mm of aluminum
- 50-70 kVp = 1.5 mm of aluminum
- 70-100 kVp = 2.5 mm of aluminum |
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Term
| 61. #6 Please define “Inherent Filtration” and list its components, as given in the notes. |
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Definition
| - 0.5 mm equivalent of aluminum due to the glass port window and the insulating oil around the glass tube |
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Term
| 62. #7 Please define “Added Filtration” and list its components, as given in the notes. |
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Definition
| - A thin aluminum sheet of aluminum at the port area between the housing and collimator and the mirror in the collimator results in 2 mm of alum. With a total of 2.5mm of equivalent aluminum |
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Term
| 63. #11 What are the three noted functions of Beam Limiters given in the notes? |
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Definition
- Changes the size and shape of the primary beam
- Decreases scatter
- increases collimation. |
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Term
| 64. #12 What are the three types of Beam Limiters noted in the notes? |
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Definition
- Aperture diaphragm
-cones and cylinders
-collimators (Semi and fully automatic) |
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Term
| 65. #33 What are the 4 types of materials used in Compensating Filters as noted in the notes? |
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Definition
- Aluminum
-copper
-opaque plastics
-liquid devices |
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Term
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Definition
| On collimator or tube head. Attenuate beam before reaching patient and reduce direct patient dose |
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Term
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Definition
| Placed behind the patient, beam is attenuated after it exposes patient and is does not reduce direct patient dose |
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Term
| Placed behind the patient, beam is attenuated after it exposes patient and is does not reduce direct patient dose |
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Definition
- Nolan Filtration System
-The Wedge
- Clear-Pb |
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Term
| 68. #39 What are the two types of Underpart Filters noted in the notes? |
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Definition
- Split screens
-boomerang filters |
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Term
| 69. #25 What are the three types of Circuits of the X-ray Machine? |
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Definition
- High voltage circuit
-filament circuit
-timer circuits |
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Term
| 70. #27 What is the purpose of the High Voltage Circuit as given in the notes? |
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Definition
| - To drive electrons from cathode to anode |
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Term
| 71. #27 What is level of the voltage needed in this circuit as given in the notes? |
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Definition
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Term
| 72. #33 Please explain “Rectification of Current” as given in the notes. |
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Definition
| - Since the x-ray tube cannot handle electrons moving in both directions the AC input must be converted to DC. This is accomplished by diodes or rectifiers that allow flow in only one direction only |
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Term
| - Half wave Rectification: |
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Definition
| Half of the overall energy is used making the x-ray inefficient. Produces x-rays in pulses (60/sec). 2 diodes |
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Term
| - Full wave Rectification : |
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Definition
| Entire waveform is used doing 120 pulses/sec. 4 diodes |
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Term
| 74. #52 Please explain a “Single Phase Generator” as given in the notes. |
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Definition
| - a single phase power AC waveform that causes the kVp to be oscillated between peak voltage and zero. This causes no x-rays at zero, soft x-rays at less than peak and hard x-rays at peak |
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Term
| 75. #57-63 Please list and explain the 2 forms of Constant Potential Generators as given in the notes. |
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Definition
| - Three phase & High frequency |
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Term
| 76. #65 What is the purpose of the Filament Circuit as given in the notes? |
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Definition
| - Generates electrons in a controllable fashion causing them to boil off at the filament |
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Term
| 77. #66 Please define “Space Charge” regarding “boiling off” at the Filament as given in the notes. |
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Definition
| - The electrons repel each other and limit the size of the cloud or electron number by equilibrium. The electrons repulsive strength causes the electrons to boil off, resulting in no room in the electron cloud for more electrons. |
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Term
| 78. #71 What is the purpose of the Timer Circuit as given in the notes? |
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Definition
| - Controls exposure time to which high-voltage and filament circuits are activated |
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Term
| 79. #3 Please List the 4 primary factors of exposure given in the notes. |
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Definition
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Term
| 80. #4 Explain the function of the kVp factor of exposure as given in the notes. |
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Definition
| - Determines how fast the electrons travel across the x-ray tube and the quality of the x-ray beam |
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Term
| 81. #8 Explain the function of the mA factor of exposure as given in the notes. |
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Definition
| - Determines the rate of flow of electrons toward the anode and the quantity of x-rays produced |
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Term
| 82. #9 Please explain the effect of doubling the mA has on the number of electrons produced at the cathode and the number of X-rays produced consequently, as given in the notes. |
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Definition
| - It doubles the number of electrons striking the anode thereby doubling the number of x-rays produced. Also doubles the darkness of the film and increases the tube load |
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Term
| 83. #10 Please explain the effect of doubling the Time (s) has on the number of electrons produced at the cathode and the number of X-rays produced consequently, as given in the notes. |
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Definition
| - Doubles the number of x-rays produced by doubling the number of electrons hitting the anode |
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Term
| 84. #17 & 19 Please explain “distance” regarding the Inverse Square Law as given in the notes. |
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Definition
| - The distance affects the number of x-rays reaching the film. The number of x-rays reaching the film is inversely proportional to the square of the distance from the source |
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Term
| 85. #30 How much of the kinetic energy of the high speed electron at the tube are converted to Heat vs. X-ray as given in the notes? |
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Definition
| - 99% is converted to heat |
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Term
| 86. #30 How is the kVp, mA & Time related to the Heat produced in the tube as given in the notes? |
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Definition
| - Heat produced is directly proportional to the kVp, mA and time used for any given exposure or multiple exposure |
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Term
| 87. #33 How does Vaporization of the tungsten metals cause failure of the tube as given in the notes? |
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Definition
| - From the excessive heat using high mAs. |
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Term
| 88. #41 & 42 Please explain the procedure for “Warming up the Anode” as given in the notes. |
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Definition
- Two successive exposures with the collimator closed:
The first at 50 mA, 50 kVp and 1/30 sec.
The second at 100 mA, 50 kVp and 1/30 sec |
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Term
| 89. #14 Please define Primary Radiation (beam) as given in the notes. |
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Definition
| - X-rays produced in and emitted from the x-ray tube. They diverge in a forward direction from the focal spot |
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Term
| 90. #14 Please define Central Ray as given in the notes. |
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Definition
| - The central point of the primary beam that exits the port window at right angles to the tube and is directed at the center of the structure to be radiographed and to the center of the film. Lowest projectional distortion occurs here. |
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Term
| 91. #15 Please define Secondary Radiation as given in the notes. |
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Definition
| - When primary x-rays interact with atoms within the patient or surrounding objects, releasing new electromagnetic radiation |
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Term
| 92. #15 Please define Scatter Radiation as given in the notes. |
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Definition
| - Results when primary x-rays are deflected and scattered in a different direction. Does not produce a new x-ray but is a primary x-ray that has lost its energy. |
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Term
| 93. #25–27 Please define Bremsstrahlung Interactions (radiation) as given in the notes. |
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Definition
| - Occurs when the electron passes near the nucleus of the atom and the positive charge of the nucleus deflects the electron from its path. Causes a decrease in kinetic energy of the electron, and the lost energy becomes heat manifested as a weak x-ray photon. Electrons give up only part of their energy with each interaction unless there is a nuclear interaction which results in an x-ray with energy equal to that of the kVp used. |
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Term
| 94. #29-31 Please define Characteristic Interactions (radiation) as given in the notes. |
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Definition
| - Occurs when the incident electron ejects an orbital electron from an inner shell of the atom. It leaves a hole and the atom becomes unstable, so an outer shell electron moves in to fill the hole. This results in the production of an x-ray photon. The energy of the x-ray produced is equal to the difference between the binding energy of the K & L shells, or whichever shell electron jumps to fill the hole. |
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Term
| 95. #38 What are the 3 interactions with matter that occur during beam attenuation, as given in the notes? |
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Definition
- Absorption
-scattering
-photon transmission |
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Term
| 96. #43 What is the effect of a High kVp and Low mAs regarding patient dose reflective of Differential Absorption? |
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Definition
| - Gives the patients lower doses |
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Term
| 97. #45 Describe the Compton Effect and explain what the probability of the Compton Effect is dependent on, as given in the notes. |
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Definition
| - causes scatter due to X-ray photons not immediately absorbed by the tissues. The probability is dependent on the energy of the incoming photon and the composition of the tissue |
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Term
| 98. #48 Which type of tissue causes more Compton Effect, as given in the notes? |
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Definition
- Hard tissues like teeth and bone absorb more x-ray than soft tissue.
-Soft tissues (esp. water density) allow partial penetration resulting in scatter.
-Air allowed complete penetration |
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Term
- Effective focal spot: ___________
The smaller the effective focal spot, the better quality of radiograph. |
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Definition
| size directly under the target. |
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Term
| What is the relationship to “penumbra” and Large focus: |
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Definition
| - More penumbra and less detail (lumbar and chest) |
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Term
| How does the focal spot size relate to the sharpness or unsharpness of recorded detail on the film Small focal spot: |
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Definition
| - Increases sharpness, causing an increased recorded detain |
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Term
| Three phase Constant potential energy: |
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Definition
| uses 3-phase power to reduce the ripple effect. Results in a more efficient beam and a nearly constant high voltage. |
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Term
| High frequency Constant potential energy: |
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Definition
| Eliminates the wave ripple effect. Causing less patient exposure to soft x-rays and a faster exposure time. |
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