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RT 209 > 6. X-ray Circuit > Flashcards

6. X-ray Circuit Flashcards

1
Q

Primary Circuit

A

Main power switch, circuit breakers, the autotransformer, the timer circuit, primary side of the step-up transformer

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2
Q

Secondary Circuit

A

Secondary side of the step-up transformer, the milliampere meter, a rectifier bank, and the x-ray tube (except for the filaments)

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3
Q

Filament Circuit

A

Rheostat, step-down transformer, the filaments

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4
Q

incorporates a meter to measure the voltage provided to the x-ray machine and a control to adjust that voltage to precisely 220 volts

A

Line Compensator

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5
Q

included in the primary circuit to protect against short circuits and electric shock

A

Circuit Breakers

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6
Q

is an adjustable transformer controlled by the kVp selector on the operating console

A

Autotransformer

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7
Q

operators in the principle of self-induction

A

Autotransformer

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8
Q

Autotransformer sometimes called the

A

kVp selector

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9
Q

primary purpose is to provide a voltage that will be increased by the step-up transformer to produce the kilovoltage selected at the operating console

A

Autotransformer

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10
Q

the radiographer controls the ______ through the kVp selector on the operating console, and through this directly determines the voltage applied to the x-ray tube to produce x-rays

A

Autotransformer

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11
Q

when a radiographer selects a kVp setting, he or she determines the number of turns on the _______ to be included in the circuit element and with it the output voltage

A

secondary side

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12
Q

used to increase the voltage from the autotransformer to the kilovoltage necessary for x-ray production

A

Step-up Transformer

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13
Q

not adjustable and increases the voltage from the autotransformer by a fixed amount

A

Step-up Transformer

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14
Q

consists of mechanical and electronic devices whose action is to “make” and “break” the high voltage across the x-ray tube

A

Timer Circuit

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15
Q

cause the x-ray to emit x-rays for a specific time as determined by the radiographer or by AEC

A

Exposure Timers

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16
Q

controls the length of exposure

A

Exposure Timers

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17
Q

simple devices use in some portable and dental units

A

Mechanical Timers

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18
Q

operates by clockwork

A

Mechanical Timers

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19
Q

inexpensive but not very accurate

A

Mechanical Timers

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20
Q

exposure times greater than 250 ms

A

Mechanical Timers

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21
Q

minimum exposure time possible 1/60 second (17 ms)

A

Synchronous Timers

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22
Q

most sophisticated, most complicated, most accurate

A

Electronic Timers

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23
Q

used for rapid serial exposures

A

Electronic Timers

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24
Q

exposure time as small as 1 ms

A

Electronic Timers

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25
Q

wide range of time intervals

A

Electronic Timers

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26
Q

based on the time it takes to charge a capacitor through a variable resistor

A

Electronic Timers

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27
Q

designed for accurate control of tube current and exposure time

A

mAs Timers

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28
Q

terminated the exposure once desired mAs is attained

A

mAs Timers

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29
Q

located in the secondary circuit

A

mAs Timers

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30
Q

automatically terminates the exposure when sufficient radiation to provide the required optical density has reached the image receptor

A

Automatic Exposure Control

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31
Q

method used to check the accuracy of exposure timer

A

Spinning Top Test

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32
Q

is a device placed in the secondary circuit that monitors x-ray tube current

A

mA meter

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33
Q

____ rectifiers are commonly used

A

solid-state

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34
Q

is responsible for converting the low voltage from the electric power company into a kilovoltage of proper waveform

A

High-Voltage Generator

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35
Q

High-voltage generator contains the following three primary parts:

A
  • High-voltage transformer
  • Filament transformer
  • Rectifiers
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36
Q

is a step-up transformer

A

High Voltage-transformer

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37
Q

The secondary voltage is greater than the primary voltage because the number of secondary windings is greater than the number of primary windings

A

High Voltage-transformer

38
Q

the ratio of the number of secondary windings to the number of primary windings

A

Turns Ratio

39
Q

is the process of converting alternating voltage to direct voltage and therefor alternating current to direct current

A

Rectification

40
Q

property of an x-ray tube which means that it acts as a valve permitting the flow of current in only one direction, from the cathode to the anode

A

Self-rectification

41
Q

represents condition in which the voltage is not allowed to swing negatively during the negative half of its cycle

A

Half-wave rectification

42
Q

contain zero, one, or two diode

A

Half-wave rectification

43
Q

x-ray output is pulsating, with 60 x-ray pulses per second

A

Half-wave rectification

44
Q

in a full-wave rectified circuit the negative half cycle corresponding to the inverse voltage is reversed so that a positive voltage is always directed across the x-ray tube

A

Full-wave rectification

45
Q

contains at least 4 diodes

A

Full-wave rectification

46
Q

x-ray output – 120 x-ray pulses per second

A

Full-wave rectification

47
Q

results in pulsating x-ray beam

A

Single-Phase Power

48
Q

alternate swing from zero to maximum potential 120 times per second

A

Single-Phase Power

49
Q

low energy, low penetrability, low diagnostic value

A

Single-Phase Power

50
Q

generated three simultaneous voltage waveforms out of step with one another

A

Three-Phase Power

51
Q

voltage across x-ray tube is nearly constant and never drops to zero during exposure

A

Three-Phase Power

52
Q

requires additional size and cost

A

Three-Phase Power

53
Q

can be place in the x-ray tube housing

A

High-Frequency Generator

54
Q

produce nearly constant potential

A

High-Frequency Generator

55
Q

improves image quality

A

High-Frequency Generator

56
Q

lower patient dose

A

High-Frequency Generator

57
Q

are high-speed switches, or choppers, that convert DC into a series of square pulses

A

Inverter Circuits

58
Q

used by a high-frequency voltage generation

A

Inverter Circuits

59
Q

Capacitor Discharge Generator uses ____ battery

A

nickel-cadmium (NiCd)

60
Q

during capacitor discharge, the voltage falls approximately

61
Q

delivers the maximum possible mA for the selected kVp by considering the instantaneous heat load characteristics of the x-ray tube

A

Falling-load capability

62
Q

This delivers the desired amount of radiation to the image receptor in the shortest possible exposure time

A

Falling-load capability

63
Q

works on the principle that a small current is drawn from the mains to charge a capacitor before the x-ray exposure, and this capacitor is allowed to discharge through the x-ray tube during exposure

A

capacitor discharge mobile

64
Q

is the variation in peak voltage waveform

A

Voltage Ripple

65
Q

100% voltage ripple

A

Single-phase Generator

66
Q

the voltage varies from zero to its maximum value

A

Single-phase Generator

67
Q

3-phased, 6 pulse generator = ___ voltage ripple

68
Q

3-phased, 12-pulse generator= ___ voltage ripple

69
Q

High-Frequency Generator less than ___ voltage ripple

70
Q

POWER RATING

A 
Power = current x potential
Watts = amperes x volts
71
Q

when specifying high-voltage generators, the industry standard is to use the maximum tube current (mA) possible at 100 kVp for an exposure of 100 ms

A

Maximum Available Power

72
Q

a variable resistor controlled by the mA selector on the operating console

73
Q

when the radiographer adjusts milliamperage on the operating console, he or she is adjusting the _____ and ultimately the amount of current applied to the filament (filament current) in the x-ray tube

74
Q

the higher milliamperage station number, the _____ resistance

75
Q

the goal of the filament circuit is to literally boil electrons out of the filament wire

A

Filament Circuit

76
Q

normally, a rather large filament current of _____ is required to produce a tube current in the range of milliamperes

A

5 to 7 amperes

77
Q

controls filament temperature

78
Q

used in filament circuit to increase the current by reducing the voltage that is applied to the filament

A

Step-down Transformer

79
Q

the purpose is to control the degree and duration that the filament is heated, which in turn controls the number of electrons boiled off that will ultimately become the tube current

A

Filament Circuit

80
Q

represented on the operating console by the “large focal spot” and “small focal spot”

81
Q

PRINCIPLES OF CIRCUIT OPERATION

A
  • The kVp selected adjusts the autotransformer and determines the number of turns on the secondary side necessary to produce a voltage, through self-induction, that will be sent to the step-up transformer
  • The step-up transformer increases this voltage by a fixed amount and, through mutual induction, produces the kilovoltage selected on the operating console
  • This kilovoltage must be rectified
  • The filament circuit draws electricity from the autotransformer, which then travels to the rheostat
  • The selected mA station sets the resistance in the filament circuit
  • From the rheostat, electricity travels to the step-down transformer
  • The kilovoltage applied to the x-ray tube creates a large positive charge on the anode and a large negative charge in the cathode
82
Q

Allows radiographer to control the x-ray tube current and voltage so that the useful x-ray beam is of proper quality and quantity

A

Operating Console/Control Panel

83
Q

refers to the number of x-rays or intensity of the beam usually expressed in mR or mR per mAs

84
Q

refers to the penetrating qualities of the x-ray beam an is expressed by kVp or HVL

85
Q

FACTORS THAT AFFECT X-RAY QUANTITY

A
  • mAs
  • kVp
  • Distance
  • Filtration
86
Q

FACTORS THAT AFFECT X-RAY QUALITY

A
  • kVp

* Filtration

87
Q

Some Basic Controls for Every Panel

A
  • On/off switch
  • mAs selection
  • kVp selection
  • Table or wall unit activation
  • Exposure switch
  • mAs and kVp meters
88
Q

EXTENDING TUBE LIFE

A
  • X-ray tube life may be extended by using minimum radiographic factors of ma, kVp, and exposure time appropriate for each examination
  • Use of faster image receptors
  • Excessive heat results in reduced x-ray tube life
89
Q

WARM UP PROCEDURES

A
  • Prepares the x-ray tube to receive high heat load
  • An example of a warm-up technique is an initial exposure of 50 kVp, 100 mA, at 1/30 second followed by a second exposure in which the mA is raised to 200
90
Q

OTHERS WAYS OF EXTENDING TUBE LIFE

A
  • Minimize filament boost (preparation) time
  • Limit rotor/start/stop operations
  • Use lower tube current (mA)
  • Do not make a high mA exposure on a cold tube
  • Adhere to rating charts and anode heating and cooling curves
  • Limit operations to 80% of maximum single exposure ratings
  • Do not exceed the anode thermal capacity or dissipation rate of the target
  • Do not rotate the tube housing rapidly from one position to another
  • Avoid long intervals between spot-films
91
Q

X-RAY TUBE AGING

A
  1. Deposition of Filament Tungsten
  2. Produces Gas (Gassy Tube)
  3. Punctured Tube
  4. Careless
  5. Damages to Anode
  6. Damages to Rotor and Bearings
  7. Damages to Filament
  8. Damages to Tube Housing
  9. Damages to Stator

RT 209 (11 decks)

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