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PRE > The X-Ray Tube (Chapter 5) > Flashcards

The X-Ray Tube (Chapter 5) Flashcards

1
Q

What are the internal X-ray tube components?

A

Cathode and Anode

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2
Q

What are the external X-ray tube components?

A
  1. Support structure
  2. Protective housing
  3. Glass or metal enclosure
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3
Q

X-ray production is only possible under these conditions:

A
  1. Source of electrons
  2. Appropriate target material
  3. High voltage
  4. Vacuum
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4
Q

Cathode side is _____ (negative, positive)

A

Negative

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5
Q

What is the function of a cathode?

A
  1. To produce thermionic cloud ⭐️⭐️⭐️⭐️
  2. Conduct high voltage to gap between cathode and anode
  3. Focus electron stream towards the anode
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6
Q

Cathode assembly consists of: (list 3)

A
  1. Filaments
  2. Focusing cup
  3. Associated wiring
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7
Q

What is a filament?

A

Small coil of thoriated tungsten wire

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8
Q

Why is tungsten important?

A
  1. High melting point
  2. Difficult to vaporize
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9
Q

What is the function of a filament?

A

resistance to the flow of electrons

so that the heat produced will cause thermionic emission

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10
Q

What is the space charge effect?

A

As more and more electrons are produced at the filament, their negative charges don’t allow any additional electrons

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11
Q

What does the focusing cup do?

A

Narrows the thermionic cloud

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12
Q

What is the focusing cup?

A

Small cup with wire

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13
Q

Focusing cup pulsed between negative and positive charge to remove electrons from use is called ___?

A

Grid -pulsed or Grid controlled

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14
Q

What are the functions of the anode? (List 3)

A

1.Target surface for electrons
2. Conducts high voltage from the cathode back into the X-ray generator
3. Primary thermal conductor

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15
Q

What does the Anode Assembly consist of?

A
  1. Anode (target)
  2. Stator
  3. Rotor
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16
Q

List 2 types of Anode (Targets)

A
  1. Stationary
  2. Rotating
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17
Q

Function of a rotating anode?

A
  1. Source of X-ray photons
  2. Primary thermal conductor
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18
Q

Common rotating anodes revolve at ____ ?

A

3,200 - 3,600 rpm

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19
Q

High speed anodes revolve at _____?

A

10,000 - 12,000 rpm

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20
Q

Tungsten is the metal of choice for 3 reasons

A
  1. High atomic number (74)
  2. High melting point
  3. Heat-conducting ability
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21
Q

What is tungsten’s atomic number?

A

74

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22
Q

What is pitting?

A

Normal use of a rotating anode will eventually vaporize the target track material

(Reduces the efficiency of the tube)

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23
Q

What is cracking?

A

Failure to warm the tube up to range of operation before use can crack the anode

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24
Q

What is the focal track?

A

The circular path that will be impacted by the electron stream and where the X-ray photons are produced

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25
Q

What is the actual focal spot?

A

The physical area of the focal track that is impacted by

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26
Q

What is the effective focal spot?

A

Area of the focal spot that is projected out of the tube toward the object being radiographed

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27
Q

The effective focal spot is controlled by:

A
  1. The actual focal spot
  2. Size of filament
  3. Anode target angle
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28
Q

What is the Anode Heel Effect?

A

Because of the geometry of an angled anode target, the radiation intensity is greater on the cathode side.

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29
Q

The anode heel effect is most noticeable at: (list 3)

A
  1. Short SID
  2. Large image receptor
  3. Small focal spot
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30
Q

The only part of the cathode or anode assemblies that is located outside the vacuum or the envelope

A

Stator

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31
Q

True or False

If the stator fails, the rotor will cease to turn the anode, resulting in the immediate melting of a spot on the target

A

True

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32
Q

Where is the Rotor located?

A

Located inside the stator and inside the envelope

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33
Q

The rotor revolves at _____ rpm

A

3,200 - 3,600

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34
Q

Rotor failures happen when?

A

There is high speed harmonic damage

(Between 5,000 - 7,000 rpm the harmonics produced by the rotating cuff are at a frequency capable of shattering the glass envelope)

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35
Q

What is the gyroscopic effect?

A

Basically like a spin top the rotor keeps it stable but then eventually something happens and it wobbles and falls

When the anode rotates quickly in different positions. Gyroscopic effect happens cuz it gets damaged

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36
Q

The envelope is made up of what kind of glass?

A

Heat resistant Pyrex glass

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37
Q

The primary function of the envelope ?

A

To maintain the vacuum between the cathode and anode

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38
Q

The protective housing controls: (list 3)

A
  1. Leakage and scatter radiation
  2. Isolates the high voltages
  3. Provides a mean to cool the tube
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39
Q

The protective housing is made up of :

A

Made of steel and lined with lead

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40
Q

When x-ray photons are produced at the anode, they are emitted _____ (in all directions)

A

Isotropically

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41
Q

The primary beam consists of:

A

Photons emitted through the window

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42
Q

Leakage radiation must not exceed _____ mR/hr at ____ meter

A

100 mR/hr at 1 meter

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43
Q

Off focus or extra focal radiation is:

A

Photons that were not produced at the focal spot

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44
Q

What is ghosting?

A

Ghosting in an X-ray tube is the appearance of faint, transparent images from previous X-ray exposures on a new X-ray image, caused by residual radiation.

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45
Q

High voltage electrons striking the focal spot produce ____ electrons or photons

A

Scattered

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46
Q

List 3 cathode filament materials:

A
  1. Tungsten
  2. Rhenium
  3. Molybdenum
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47
Q

Filament materials are chosen primarily for their___?

A

High melting points & difficult to vaporize

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48
Q

List 3 things that would affect the production of a thermionic cloud

A
  1. Filament diameter
  2. Filament length
  3. Filament temperature
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49
Q

A filament may break due to ____

A

Vaporization

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50
Q

Driving the thermionic cloud from the cathode to the anode requires ____

A

High - Voltage

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51
Q

The cathode focusing cup has a _____ charge

A

Negative

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52
Q

As more and more electrons build up in the area of the filament, their negative charges oppose the emission of additional electrons. This phenomenon is known as ______

A

Space charge effect

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53
Q

X-ray photon production occurs at the

A

Anode

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54
Q

Tungsten is the material of choice for the source of X-ray photons primarily because of its

A

High atomic number
Heat conductivity ability
High melting point

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55
Q

Pitting of the anode commonly occurs ____

A

With extended use

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56
Q

Melting of the anode commonly occurs when …

A

When the stator fails and the rotor ceases to turn

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57
Q

Cracking of the anode typically occurs when …

A

When a cold anode is hit with a high kVp exposure

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58
Q

The exact point on the anode where the x-ray beam comes out is the ____

A

Effective focal spot

59
Q

The physical area of a rotating anode focal track, affected by the cathode electron beam, is the ____

A

Actual focal spot

60
Q

The area of the focal spot that is projected out of the tube toward the object being radiographed is the

A

Effective focal spot

61
Q

The actual focal spot is controlled by the

A

Length of the filament

62
Q

The most common diagnostic radiography x-ray tube target angle is ___ degrees

A

12

63
Q

As the actual focal spot size increases, the effective focal spot size _____

(Decreases, increases, doesn’t change)

A

Increases (they are directly related)

64
Q

As the angle of the anode increases and the incident electron beam size remains the same, the effective focal spot size ____

(Decreases, increases, doesn’t change)

A

Increases

65
Q

The use of the line-principle causes a problem knows as the _____ effect

A

Anode heel effect

66
Q

The only portion of the anode assembly placed outside the vacuum of the glass envelope is the ____

A

Stator (magnets that turn rotor)

67
Q

The function of the stator and rotor assembly is to ___

A

Rotate the anode

68
Q

To increase the thermal loading capacity of the anode, the X-ray tube manufacturers must ____

A

Bond graphite to the back of the anode

69
Q

The protective housing controls leakage and scatter radiation through ______

A

Absorption

70
Q

Insulation of the high voltage components of the tube and absorption of the heat produced by X-ray production are achieved through the use of _____

A

Dielectric oil

71
Q

What type of radiation is composed of photons NOT produced at the actual focal spot?

A

Off-focus and extra-focal

72
Q

Leakage radiation from the lead-lined housing must NOT exceed

A

100 mR/hr at 1 meter

73
Q

Radiation intensity is greater at the (anode/cathode) __________________________ side of the x-ray beam.

A

Cathode

74
Q

The ANODE HEEL EFFECT is more noticeable with a (long/short) ______________________________ SID and a large Image Receptor.

A

Short

75
Q

What 4 things are needed to make x-rays?

A
  • source of electrons
  • an appropriate target material
  • high voltage
  • vacuum
76
Q

What two things control the size of the EFFECTIVE Focal Spot?

A
  1. Size of the actual focal spot (which is controlled by the size of the filament)
  2. Anode target angle
77
Q

Decreasing the size of the filament will decrease the size of the:

A

Focal spot

78
Q

The cathode side of the x-ray tube has a (negative/positive/neutral) __________________charge.

A

Negative

79
Q

In an x-ray tube, the smaller the coil (filament), the (smaller/larger) __________________ the structure that can be imaged.

A

Smaller

80
Q

Turning something into a gas is called:

A

Vaporization

81
Q

Inside the x-ray tube, the component that is a shallow depression in the cathode assembly is called the:

A

Focusing cup

82
Q

A space from which air and gases have been removed is called a (an):

A

Vacuum

83
Q

Tungsten is the material of choice for the FILAMENT because it:

A

Has a high melting point and is difficult to vaporize

84
Q

Rotating anode x-ray tubes allow (bigger/smaller) ________________________ exposures than stationary anode x-ray tubes.

A

Bigger

85
Q

Large filaments (large focal spots) are used to image (larger/smaller) ______________________ body parts because the small filaments can’t take the stress of making big exposures on big body parts.

A

Larger

86
Q

A cloud of electrons that forms when thermionic emission occurs is called a (an):

A

Thermionic cloud

87
Q

Placing ______________________ on the back of rotating anodes can double the heat-loading capabilities

A

Graphite

88
Q

The material of choice for the filament is usually _________________________________________ wire.

A

Tungsten

89
Q

Routinely delaying the exposure (holding the rotor too long) while the filament is heating up (enduring maximum current) can shorten the tube life by about _________% to _________%.

A

50% to 60%

90
Q

The x-ray tube consists of a cathode, anode, glass envelope and the:

A

Protective housing

91
Q

When electrons are set free from the x-ray tube filament we sometimes say that they have been ____________________ off.

A

Boiled

92
Q

The focusing cup is made of:

A

Nickel

93
Q

An x-ray tube that is used to pulse the x-rays on and off quickly is called:

A

Grid pulsed or grid controlled

94
Q

Increasing the speed that the anode rotates will (decrease/increase/not affect) _____________________ the heat loading capabilities of an x-ray tube.

A

Increase

95
Q

What happens to vaporized electrons inside the x-ray tube? (List 2 things)

A

A. Reduces the tube vacuum
thus causing the tube to become gassy.

B. Deposit on the inside of the glass envelope

96
Q

Most x-ray tubes have 2 filaments and this is known as a (an) _____________________________ FOCUS.

A

Dual Focus

97
Q

One of the primary causes of premature tube failure is the radiographer’s habit of holding the:

A

ROTOR SWITCH TOO LONG BEFORE MAKING AN
EXPOSURE

98
Q

What are the two things that the vaporized electrons that coat the inside of the x-ray tube can cause?

A

A. HIGH-VOLTAGE ARCHING

B. INCREASED FILTRATION OF THE PRIMARY X-RAY BEAM WHICH DECREASES TUBE EFFICIENCY

99
Q

What makes the electrons move across the x-ray tube from cathode to anode?

A

High voltage

100
Q

Any photons that escape from the x-ray tube housing except at the port are called:

A

Leakage radiation

101
Q

The anode side of the x-ray tube has a (negative/positive/neutral) _________________ charge

A

Positive

102
Q

When the target angle is decreased, (larger/smaller) __________________ Focal Spots can be achieved.

A

Smaller

103
Q

The special glass used in x-ray tubes is:

A

Pyrex

104
Q

In addition to tungsten as a target material, ____________________________________ is added to provide greater elasticity when the focal track expands rapidly due to the intense heat.

A

Rhenium

105
Q

Inside the x-ray tube, the coil of wire is known as the:

A

Filament

106
Q

The roughening of the anode during normal use is called:

A

Pitting

107
Q

Pitting (decreases/increases) __________________ the efficiency of an x-ray tube.

A

Decreases

108
Q

Special high speed anodes rotate between __________ - __________ r.p.m.

A

10,000 to 12,000

109
Q

The x-ray tube component that is used to direct the electron cloud into a stream of electrons as it heads for the anode is called the:

A

Focusing cup

110
Q

Failure to warm up the x-ray tube may cause the anode to:

A

Crack

111
Q

Standard x-ray tube anodes normally rotate between __________ - __________ r.p.m.

A

3,200 to 3,600

112
Q

The vast majority of high-output x-ray tubes are now made with __________________________ envelopes.

A

Metal

113
Q

What are the three main reasons that tungsten is the main material of choice for the x-ray tube TARGET?

A
  1. High atomic number
  2. High melting point
  3. Heat conducting ability
114
Q

The ______________________________ Principle is used to reduce the effective area of the focal spot

A

Line - focus principle

115
Q

The line-focus principle is used to reduce the effective area of the ______

A

Focal spot

116
Q

The ______________________ Focal Spot is used to describe the area of the focal spot that is projected out of the x-ray tube towards the object being radiographed.

A

Effective focal spot

117
Q

The ______________________________ permits the best resolution of detail while permitting as large an actual area as possible to act as a target (to increase thermal conductivity).

A

Line-focus principle

118
Q

The term ________________________ refers to a very small Focal Spot, one that is a fraction of a millimeter in size.

A

Fractional focal spot

119
Q

As the mA increases, so does the size of the Focal Spot. This is called:

A

Blooming

120
Q

Some specialized mammography x-ray tubes use __________________________ as the target material.

A

Molybdenum

121
Q

When the target angle is less than ______ degrees, the Effective Focal Spot is smaller than the Actual Focal Spot.

A

45 degrees

122
Q

The point inside the x-ray tube where the x-ray photons are created is called the:

A

TARGET, FOCUS, FOCAL POINT, FOCAL SPOT or the FOCAL TRACK

123
Q

The ANODE HEEL EFFECT is more noticeable with (large/small) _________________ Image Receptors (or x-ray films).

A

Large

124
Q

Many x-ray tubes have a thinned area of the glass called the:

A

Window

125
Q

In addition to tungsten, what two other materials are desirable for use as the x-ray tube filament?

A

Rhenium and molybdenum

126
Q

What is the process called that produces particles that deposit on surfaces and reduces the vacuum within the x-ray tube?

A

Vaporization

127
Q

Passing an electric current through a filament to the point where it heats up and causes electrons to leave the surface of the filament wire is called:

A

Thermionic emission

128
Q

What causes the electrons in a thermionic cloud to move across the x-ray tube from cathode to anode?

A

High voltage

129
Q

Rough handling of an old x-ray tube with a thin ____________________________ can cause it to break prematurely.

A

Filament

130
Q

What part of the x-ray tube is responsible for narrowing the thermionic cloud as it is driven towards the anode?

A

Focusing cup

131
Q

When the rotor is activated during an exposure, a higher current is sent to the filament - - - this increases the filament heating and is what causes most of the _________________________________ of the filament.

A

Vaporization

132
Q

The (faster/slower) _____________________ the anode rotates, the better the heat dissipation.

A

Faster

133
Q

Rotating anodes disks are composed of:

A

Molybdenum

134
Q

A(An) ________________________-relieved anode dissipates heat much more efficiently than a standard x-ray tube anode.

A

Stress

135
Q

The S.I.D. (Source to Image Receptor Distance) is measured from the ___________________________ to the Image Receptor

A

TARGET, FOCUS, FOCAL POINT, FOCAL SPOT or the FOCAL TRACK

136
Q

Rotating anode x-ray tubes have much greater ________________________ capacities than stationary anode x-ray tubes.

A

Heat loading

137
Q

The Line – Focus Principle is used to ___________ the effective area of the focal spot.

A

Reduce

138
Q

The use of the Line-Focus Principle causes a problem known as the:

A

Anode heel effect

139
Q

The intensity of radiation emitted by the x-ray tube target varies by about _________% between the anode side and the cathode side.

A

45%

140
Q

With the Anode Heel Effect, the (anode/cathode)______________________ side has a more intense x-ray beam.

A

Cathode

141
Q

If a high-speed anode tube-housing is quickly rotated from one position to another (for example, from horizontal to vertical), the ________________________ Effect can cause trauma to the anode disk and bearings, causing destruction of the tube.

A

Gyroscopic

142
Q

A metal envelope x-ray tube has a longer tube life because they eliminate the problems of:

A

Tungsten evaporation

143
Q

What are the three functions of the positive side of the x-ray tube? (Anode side)

A

A. target surface
B. primary thermal conductor
C. Conducts the high voltage from the cathode back into the x-ray generator

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