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113 > Finals | Xray Tube > Flashcards

Finals | Xray Tube Flashcards

1
Q

A special type of diode (anode & cathode)

A

X-ray Tube

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2
Q

What is a diode?

A

Any electronic tube with two electrodes

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3
Q

An x-ray tube is a special type of a/n —

A

diode

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4
Q

Electrodes

A

Cathode and anode

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5
Q

The xray tube is (1) seen by (2)

A
  1. rarely
  2. radiologic technologists
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6
Q

What energy does an xray tube convert?

A

Converts electrical energy to electromagnetic energy

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7
Q

Xray Tube External Components

A
  • Support Structure
    • Ceiling Support System
    • Floor-to-Ceiling Support System
    • C-Arm Support System
  • Protective Housing
  • Glass/Metal Enclosure
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8
Q

Xray Tube Internal Components

A
  • Cathode
  • Anode
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9
Q

Xray tube is contained in a (1) and therefeore (2)

A
  1. protective housing
  2. inaccessible
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10
Q

Two primary parts of the xray tube

A
  1. Cathode
  2. Anode
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11
Q

Most frequently used support system

A

Ceiling support system

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12
Q

Consists of two perpendicular sets of ceiling-mounted rails. This allows for both longitudinal and transverse travel of the x-ray tube.

A

Ceiling support system

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13
Q

Ceiling support system consists of two perpendicular sets of (1). This allows for both (2) and (3) travel of the x-ray tube.

A
  1. ceiling-mounted rails
  2. longitudinal
  3. transverse
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14
Q

Other positions can be chosen and locked by the radiologic technologist.

A

Ceiling support system

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15
Q

Some ceiling-supported x-ray tubes have a single control that removes all (1), allowing the tube to (2).

A
  1. locks
  2. “float.”
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16
Q

Some — have a single control that removes all locks, allowing the tube to “float.”

A

ceiling-supported x-raytubes

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17
Q

Has a single column with rollers at each end, one attached to a ceiling-mounted rail and the other attached to a floor-mounted rail.

A

Floor-to-Ceiling Support System

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18
Q

Floor-to-Ceiling Support System has a single column with (1) at each end, one attached to a (2) and the other attached to a (3).

A
  1. rollers
  2. ceiling-mounted rail
  3. floor-mounted rail
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19
Q

A variation of a floor-to-ceiling support system is —

A

floor support system

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20
Q

Interventional radiology suites often are equipped with these

A

C-Arm Support System

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21
Q

Where is the IR attached in a C-Arm Support System?

A

The image receptor is attached to the other end of the C-arm from the x-ray tube

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22
Q

Variations of the C-Arm Support System

A

L-arm or U-arm support

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23
Q

When x-rays are produced, they are emitted (1), that is, with (2) in (3).

A
  1. isotropically
  2. equal intensity
  3. all directions
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24
Q

Only x-rays emitted through the special section of the x-ray tube called the — are used

A

window

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25
Q

X-rays emitted through the window

A

Useful beam

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26
Q

X-rays that escape through the protective housing

A

Leakage radiation

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27
Q

Contributes nothing in the way of diagnostic information and result in unnecessary exposure of the patient and the radiologic technologist

A

Leakage radiation

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28
Q

Leakage radiation result

A

Unnecessary exposure of patients and radiologic technologist

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29
Q

What does the protective housing provide?

A
  1. Mechanical support for the xray tube and protects it from damage caused by rough handling
  2. Contains diala oil that serves as both insulator against electric shock and as a thermal cushion to dissipate heat
  3. Has cooling fans to air cool the tube or the oil in which the x-ray tube is immersed
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30
Q

Functions of the diala oil

A

INSULATOR against electric shock and THERMAL CUSHION to dissipate heat

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31
Q

An x-ray tube is an electronic (1) with components contained within a (2) or (3) enclosure

A
  1. vacuum tube
  2. glass
  3. metal
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32
Q

An enclosure is relatively large, perhaps (1) long and (2) in diameter

A
  1. 30 to 50 cm
  2. 20 cm
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33
Q

The glass enclosure is made of (1) to enable it to (2) the tremendous heat generated.

A
  1. Pyrex glass
  2. withstand
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34
Q

Metal enclosure tubes maintain a constant (1) between the (2) of the tube current and the enclosure. Therefore, they have a longer life and are less likely to fail. Virtually all (3) x-ray tubes now use metal enclosures

A
  1. electric potential
  2. electrons
  3. high-capacity
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35
Q

Have a longer life and are less likely to fail.

A

Metal enclosure tubes

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36
Q

The x-ray tube window is an area of the glass or metal enclosure, approximately (1), that is (2) and through which the (3) of x-rays is emitted

A
  1. 5 cm^2
  2. thin
  3. useful beam
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37
Q

Disadvantage of a glass enclosure

A

More likely to fail, lesser tube life

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38
Q

A segment of glass that is thinner than the rest of the glass envelope

A

Tube window

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39
Q

Contributes to inherent filtration

A

Glass enclosure

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40
Q

The cathode is the (1) side of the x-ray tube; it has two primary parts, a (2) and a (3)

A
  1. negative
  2. filament
  3. focusing cup
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41
Q

A coil of wire similar to that in a kitchen toaster, but it is much smaller

A

Filament

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42
Q

Diameter and length of the filament

A

approximately 2 mm in diameter
1 or 2 cm long.

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43
Q

Emits electrons when it is
heated

A

Filament

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44
Q

When the current through the filament is sufficiently high, the (1) of the filament atoms are (2) and (3) from the filament. This phenomenon is known as (4).

A
  1. outer-shell electrons
  2. “boiled off”
  3. ejected
  4. thermionic emission
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45
Q

Filament composition

A

Thoriated tungsten

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46
Q

Reason why the filament is made up of thoriated tungsten

A
  1. Higher thermionic emission than other metals
  2. High melting points of 3410°, therefore is unlikely to burn out like the filament of a light bulb
  3. Tungsten does not vaporize easily
47
Q

Tungsten does not vaporize easily. If it did, the tube would become (1) quickly, and its (2) would be coated with tungsten

A
  1. gassy
  2. internal parts
48
Q

If vaporized, tungsten can cause (1) and can lead to (2)

A
  1. arcing
  2. tube failure
49
Q

The addition of (1) to the tungsten filament enhances the efficiency of (2) and prolongs (3)

A
  1. 1% to 2% thorium
  2. thermionic emission
  3. tube life
50
Q

(1) with (2) on the inside of the glass enclosure is the most common cause of tube failure

A
  1. Tungsten vaporization
  2. deposition
51
Q

The filament is embedded in a (1) called the (2)

A
  1. metal shroud
  2. focusing cup
52
Q

Because all of the electrons accelerated from cathode to anode are electrically (1), the electron beam tends to (2) owing to (3).

A
  1. negative
  2. spread out
  3. electrostatic repulsion
53
Q

The focusing cup is (1) so that it electrostatically (2) the electron beam to a small area of the (3)

A
  1. negatively charged
  2. confines
  3. anode
54
Q

Where does the effectiveness of the focusing cup depend on?

A
  1. Focusing cup size and shape
  2. Focusing cup charge
  3. Filament size and shape
  4. Position of the filament in the focusing cup
55
Q

It serves as a grid (exposure switch) in a grid-controlled x-ray tube

A

Focusing cup

56
Q

Focusing cup serves as a (1) (exposure switch) in a (2) x-ray tube

A
  1. grid
  2. grid-controlled
57
Q

Cloud of electrons

A

Space charge

58
Q

A phenomenon of the space charge that makes it difficult for subsequent electrons to be emitted by filament because of electrostatic repulsion

A

Space charge effect

59
Q

Space charge effect is a phenomenon of the space charge that makes it difficult for subsequent electrons to be emitted by filament because of (1)

A
  1. electrostatic repulsion
60
Q

Tendency of space charge to limit emission of other electrons from filament

A

Space charge effect

61
Q

Thermionic emission at (1) and (2) can be space charge limited

A
  1. low kVp
  2. high mA
62
Q

The small focal spot is associated with the —

A

small filament

63
Q

A/n (1) is directed through the appropriate filament

A

electric current

64
Q

Used when better spatial resolution is required

A

Small focal spot

65
Q

Limiting factor of the small focal spot

A

Heating of the target is concentrated onto a smaller area

66
Q

Used when when other techniques that produce high heat are required

A

Large focal spot

67
Q

Important for high-resolution magnification radiography and mammography

A

Round focal spot

68
Q

These are possible with the rotating anode

A
  1. Higher tube current
  2. Shorter exposure time
69
Q

Positive side of x-ray tube

A

Anode

70
Q

Two types of anodes

A

Stationary and rotating

71
Q

Where are stationary anode x-ray tubes used?

A
  • Dental x-ray imaging systems
  • Portable imaging systems
  • Other special-purpose units in which high tube current and power are not required
72
Q

It is used when high tube current & power are NOT required

A

Stationary anode

73
Q

Where are rotating anode x-ray tubes used?

A

General purpose x-ray

74
Q

Why do general purpose x-ray make use of rotating anode?

A

Because they must be capable of producing high-intensity x-ray beams in a short time.

75
Q

3 functions of the anode

A
  1. Electrical conductor
  2. Mechanical support for target
  3. Thermal dissipator
76
Q

The anode also must be a good thermal dissipater. When the (1) from the cathode interact with the anode, (2) of their kinetic energy is converted into (3). This (3) must be dissipated quickly.

A
  1. projectile electrons
  2. more than 99%
  3. heat
77
Q

Most common anode materials

A

Copper (Cu-29)
Molybdenum (Mo-42)
Graphite

78
Q

Major engineering hurdle in designing higher
capacity x-ray tubes

A

Adequate heat dissipation

79
Q

Area of the anode struck by the electrons from the cathode.

A

Target

80
Q

In STATIONARY anode tubes, the target consists of —

A

tungsten alloy embedded in the copper anode

81
Q

In ROTATING anode tubes, the (1) is the target

A
  1. entire rotating disc
82
Q

TARGET

Alloying the tungsten (usually with [1]) gives it added (2) strength to withstand the stresses of (3) and the effects of repetitive (4) and (5).

A
  1. rhenium
  2. mechanical
  3. high-speed rotation
  4. thermal expansion
  5. contraction
83
Q

Mammographic targets

A

Molybdenum (Mo-42)
Rhodium (RH-45)

84
Q

High-capacity x-ray tubes have (1) or (2) layered under the tungsten target.

A
  1. molybdenum
  2. graphite
85
Q

Characteristics of Mo & Graphite

A

▪ Lower mass density than tungsten
▪ Make anode lighter & easier to rotate

86
Q

Tungsten is the material of choice for the target for general radiography for three main reasons

A
  1. Atomic number (74)
  2. Thermal conductivity nearly equal to that of copper
  3. High melting point (3410°C)
87
Q

Tungsten has a high melting point (3410°C compared with [1] for copper) and therefore can stand up under high tube current without (2) or (3)

A
  1. 1100°C
  2. pitting
  3. bubbling
88
Q

Characteristics of X-ray Targets basis

A
  1. Atomic Number
  2. K X-ray Energy (keV)*
  3. Melting Temperature (°C)
89
Q

Tungsten symbol

A

W

90
Q

Molybdenum symbol,

A

Mo

91
Q

Rhodium symbol

A

Rh

92
Q

Tungsten Z

A

74

93
Q

Molybdenum Z

A

42

94
Q

Rhodium Z

A

45

95
Q

Tungsten K X-ray Energy

A

69 keV

96
Q

Molybdenum K X-ray Energy

A

19 keV

97
Q

Rhodium K X-ray Energy

A

23 keV

98
Q

Tungsten Melting Temperature

A

3400°C/ 3410

99
Q

Molybdenum Melting Temperature

A

2600°C

100
Q

Rhodium Melting Temperature

A

3200°C

101
Q

Allows the electron beam to interact with a much larger target area; therefore, the heating of the anode is not confined to one small spot

A

Rotating anode x-ray tube

102
Q

The rotating anode x-ray tube allows the electron beam to interact with a much (1) target area; therefore, the heating of the anode is (2) to one small spot, as in a stationary anode tube.

A
  1. larger
  2. not confined
103
Q

Heat capacity can be further improved by —

A

increasing the speed of anode rotation

104
Q

Anode stem is usually made of (1) because it is a poor (2). It is also (3) so as to reduce its (4)

A
  1. molybdenum
  2. heat conductor
  3. narrow
  4. thermal conductivity
105
Q

Most rotating anodes revolve at (1) rpm (revolutions per minute). While the anodes of high-capacity x-ray tubes rotate at (2) rpm.

A
  1. 3400
  2. 10,000
106
Q

Used to turn the anode

A

Electromagnetic induction motor

107
Q

How does the anode rotate inside an enclosure with no mechanical connection to the outside?

A

An electromagnetic induction motor is used to turn the anode.

108
Q

An induction motor consists of two principal parts separated from each other by the glass or metal enclosure namely:

A
  1. Stator
  2. Rotor
109
Q

Part of the induction motor outside the glass or
metal enclosure

A

Stator

110
Q

Consists of a series of
electromagnets equally spaced around the neck of the tube

A

Stator

111
Q

Stationary coil windings

A

Stator

112
Q

A shaft inside the enclosure made of bars of
copper and soft iron fabricated into one mass

A

Rotor

113
Q

Rotating part of rotor

A

Shaft

114
Q

Rotor composition

A

Bars of copper and soft iron

113 (18 decks)

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