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RT 209 > X-Ray Machine and Tube > Flashcards

X-Ray Machine and Tube Flashcards

1
Q

is to provide a controlled flow of electrons intense enough to produce an x-ray beam appropriate for imaging

A

The function of the x-ray imaging system

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2
Q

Diagnostics x-ray imaging systems are usually operated at voltages of _________ kVp and at tube currents of _________ mA

A
  1. 25 to 150 kVp
  2. 100 to 1200 mA.
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3
Q

Types of X-ray Machine According to Purpose (6)

A
  • Fixed X-ray Apparatus
  • Mobile X-ray Apparatus
  • Portable X-ray Apparatus
  • Dental X-ray Machine
  • Mammographic X-ray Machine
  • Panoramic X-ray Machine
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4
Q

The machines which fall into this group are characterized by the fact that they require transformers of such size and output that they have to be built into the room and provided with special electrical connections to the mains.

A

Fixed X-ray Apparatus

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5
Q

The X-ray tube is connected to the transformer by high-tension cables and is mounted on some form of gantry which allows only limited movement.

A

Fixed X-ray Apparatus

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6
Q

Fixed X-ray Apparatus

Such machines are likely to be capable of an output of at least —– mA and ——- kV and in some instances much higher (1000 mA and 200 kV ).

A

300 mA and 120 kV

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7
Q

These machines have higher output than portable machines by virtue of their larger transformers and are mounted on wheels with output of 90-125kv and 40 to 300 mA.

A

Mobile X-ray Apparatus

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8
Q

Mobile X-ray Apparatus

These machines have higher output than portable machines by virtue of their larger transformers and are mounted on wheels with output of —— kV and —— mA.

A

90-125 kv and 40-300 mA

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9
Q

In machines of this type the transformers are larger to permit higher output and because of their increased weight are no longer located in the tube head but are mounted on wheels and form the best of the apparatus.

A

Mobile X-ray Apparatus

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10
Q

These sets cannot be taken apart and the tube stand and control panel are built into the apparatus.

A

Mobile X-ray Apparatus

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11
Q

Commonly used in veterinary practice because of convenient transportation.

In such machines the transformers are of small size and low weight and are located within the tube head immediately adjacent to the X-ray tube.

A

Portable X-ray Apparatus

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12
Q

The tube head itself is supported on a tube stand which may comprise either a small table top model or a considerably more substantial floor stand mounted on wheels.

A

Portable X-ray Apparatus

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13
Q

The apparatus also has a small control panel which is attached to the tube stand or the tube head or supported on a separate stand.

A

Portable X-ray Apparatus

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14
Q

What are the advantages of Portable X-ray Apparatus?

  • Relatively ——- and require ————-
  • They —— than other types of machine.
  • They are ————- and need little maintenance.
  • They can be operated from any ———– electrical point.
  • They can be ———– for use on farms or other premises.
  • They are light and —————
A
  • Relatively cheap and require little maintenance. .
  • They cost less than other types of machine.
  • They are strongly constructed and need little maintenance.
  • They can be operated from any 12 — or 15-A electrical point.
  • They can be easily transported for use on farms or other premises.
  • They are light and easily maneuvered.
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15
Q

What is the disadvantage of a Portable X-ray Apparatus

A

Because of low electrical output, these machines are of limited value in radiographic examination.

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16
Q
  • Apparatus manufactured for dental use is sometimes advocated for veterinary use because of its low price.
A

Dental X-ray Machine

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17
Q

Dental X-ray Machine

Such machines are of low output (in the region of ———) and are designed to only cover a small area of the patient.

A

10 mA and 70 kV

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18
Q

3 main Components of An X-ray Imaging System
(X, O, H)

A
  • X-ray tube
  • Operating Console
  • High voltage generator
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19
Q

A vacuum tube containing electrodes that accelerate electrons and direct them to a metal anode, where their impacts produce x-rays.

A

X-ray Tube

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20
Q

What are the External Components of the X-ray Tube

A
  • Support structure
  • Protective housing
  • Glass or metal enclosure
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21
Q

X-ray Tube

Consist of two perpendicular sets of ceiling-mounted rails.

A

Ceiling Support System

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22
Q

X-ray Tube

Has a single column with rollers at each end.

A

Floors to Ceiling Support System

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23
Q

X-ray Tube

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

A

C-arm Support System

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24
Q

X-ray Tube

Guards against excessive radiation exposure and electrical shock.

A

Proctective Housing

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25
Q

X-ray Tube

The glass is made up of pyrex to withstand the tremendous heat generated.

A

Glass or Metal Envelope

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26
Q

X-ray Tube

What material is the glass envelope made up of?

A

Pyrex

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27
Q

Is the area of the glass or metal enclosure, approximately 5 cm² , that is thin and through which the useful beam of x-rays is emitted.

A

X-ray tube window

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28
Q

X-ray tube window

X-rays emitted through the window

A

useful beam

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29
Q

X-ray tube window

X-rays that escaped through the tube housing

A

leakage radiation

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30
Q

X-ray tube window

X-rays that escaped through the tube housing

A

leakage radiation

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31
Q

X-ray tube window

Leakage radiation should not exceed ——- when operated at maximum condition.

A

100 mR/hr at 1 m

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32
Q

X-ray tube window

What are the Internal Components

A
  • Cathode
  • Anode
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33
Q

is the negative side of the x-ray tube

A

Cathode

34
Q

Two primary parts of the Cathode

A
  • filament
  • focusing cup
35
Q

Usually approximately 2mm in diameter and 1 or 2 cm long.

A

Filament

36
Q

What are the two kinds of filaments

A

small and large filament

37
Q

When the current through the filament is sufficiently high, the outer-shell electrons of the filament atoms are “boiled off” and ejected from the filament.

A

Thermionic Emission

38
Q

Filaments are usually made of thoriated tungsten because?

  • Tungsten have ————–
  • Does not ———–
  • Addition to 1% to 2% thorium to tungsten increases ——————
A
  • high melting point (3410 °C)
  • vaporize easily
  • the efficiency of thermionic emission
39
Q

Where the filaments are embedded.

A

Focusing Cup

40
Q

is used when better spatial resolution is required. Ranges from 0.1 to 1 mm

A

small focal spot

41
Q

is used when large body parts are imaged and when other techniques that produce high are
required.

A

large focal spot

42
Q

is the positive side of the x-ray tube; it conducts electricity and radiates heat and contains the target.

A

Anode

43
Q

Functions of anode assembly

A
  • Electrical conductor
  • Mechanical support
  • Thermal dissipator
44
Q

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

A

Target

45
Q

Types of Anode

A
  • Stationary anode
  • Rotating anode
46
Q

Type of Anode

Are used in dental x-ray imaging systems, some portable imaging systems, and other-purpose units in which high tube current and power are not required.

A

Stationary Anode

47
Q
  • Capable of producing high intensity x-ray beam.
  • Heat capacity can be further improved by increasing the speed of anode rotation.
A

Rotating Anode

48
Q

A rotating anode rotates at ?

A

3400 rpm and 10,000 rpm

49
Q

In stationary anode tubes
the target is —— embedded in —— and about the size of —–

A
  • tungsten alloy embedded in a copper anode.
  • 4 mm ²
50
Q

In rotating anode targets
the ——– is the target. About —–

A
  • entire rotating disc
  • 3159 mm²
51
Q

Tungsten is the material of choice for the target for general radiography for 3 main reasons
(A,T,H)

A
  • Atomic number
  • Thermal conductivity
  • High melting point
52
Q

Mammographic X-ray Tubes

  • Specialty x-ray tubes for mammography have ——- or ——— targets principally because of their low atomic number and low K characteristics x-ray energy.
  • ———— gives it added mechanical strength to withstand the stresses of high speed rotation.
  • ——- and ——- have lower mass density than tungsten, thus allowing the target easier to rotate.
A
  1. molybdenum or rhodium targets
  2. alloying tungsten (usually with rhenium)
  3. Molybdenum and graphite
53
Q

The rotating anode is powered by

A

Induction Motor

54
Q

2 parts of an Induction motor

A
  • stator
  • rotor
55
Q

Is the actual x-ray source

A

Focal spot

56
Q

Results in an effective focal spot size much less than the actual focal spot size.

A

Line-Focus Principle

57
Q

Line-Focus Principle

Diagnostic x-ray tubes have target angles that vary from approximately

A

5 to 20 degrees

58
Q

allows high anode heating with small effective focal spots. As the target decreases, so does the focal spot size.

A

Line-Focus principle

59
Q

Radiation intensity is greater on the cathode side of the x-ray field than that on the anode side.

A

Heel Effect

60
Q

Heel Effect

The smaller the ——-, the larger is the ——–

A
  • anode angle
  • heel effect
61
Q

Heel Effect

The difference in the radiation intensity across the useful beam of an x-ray field can vary by as much as —–.

A

45 %

62
Q

Electrons bounce off the focal spot and then land on other areas of the target, causing x-rays to be produced from outside of the focal spot.

A

Off Focus Radiation

63
Q

Ways How to Extend X-ray Tube Life Span

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.
64
Q

3 ways to dissipate Heat

A
  • Radiation
  • Conduction
  • Convection
65
Q

Transfer of heat by the emission of infrared radiation.

A

Radiation

66
Q

Transfer of energy from one area of an object to another.

A

Conduction

67
Q

Transfer of heat by the movement of a heated substance from one place to another.

A

Convection

68
Q

Causes of X-ray Tube Failure

A
  • Vaporized tungsten
  • Rotor bearings breakage
  • Anode pitting
  • Cracked anode
69
Q

3 types of x-ray tube rating charts significant to radiologic technologist

A
  • Radiographic rating chart
  • Anode cooling chart
  • Housing cooling chart
70
Q
  • Conveys radiographic techniques which are safe and unsafe for tube operation.
  • Used to determine the length of time required for complete cooling after any level of heat input
A

Radiographic Rating Chart

71
Q
  • Contains the thermal capacity of an anode and its heat dissipation characteristics.
A

Anode Cooling Chart

72
Q

Anode Cooling Chart

conventionally measured in units of calories

A

Thermal energy

73
Q

Anode Cooling Chart

In x-ray applications, thermal energy is measured in

A

heat units (HU)

74
Q

Heat Units (HU)

One heat unit is equal to the product of ——-.

A

1 kVp, 1 mA, and 1s.

75
Q

The capacity of the anode and the housing to store heat is measured

A

heat units

76
Q

Anode Cooling Chart

Single-Phase

A

HU= kVp x mA x s

77
Q

Radiographic examination of the lateral lumbar spine with a single-phase imaging system requires 98 kVp, 120 mAs. How many heat units are generated by this exposure?

A

11,760 HU

78
Q

examination is performed with a single-phase imaging system at 76 kVp and 1.5 mA for 3.5 min. How many heat units are generated?

A

23,940 HU

79
Q

Anode Cooling Chart

Three-phase/High-Frequency

A

HU=1.4 x kVp x mAxs

80
Q

Six sequential skull films are exposed with a three-phase generator operated at 82 kVp, 120 mAs. What is the total heat generated?

A

82,656 HU

81
Q

Heat Units conversion to Joules

1 HU = —-
1 J = —–

A

1 HU = 1.4 J
1 J = 0.7 HU

82
Q
  • Radiographic x-ray tube housings usually have maximum heat capacities in the range of several million heat units.
  • Complete cooling after maximum heat capacity requires from 1 to 2 hours.
A

Housing Cooling Chart

RT 209 (4 decks)

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