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Radphy 2 > Xray Tube Part 1 > Flashcards

Xray Tube Part 1 Flashcards

0
Q

Travel of the xray

A

Cathode
Aluminum cross and anode
fluorescent image
dark shadow

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1
Q

Demonstation by crookes, it travels in straight lines

A

Cathode rays

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2
Q

Dr. Roentgen used _____ to make the first xray image

A

Crookes-hittorf tube

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3
Q

It was a major advancement in tube design

A

Coolidge Hot Cathode Tube

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4
Q

Two major hazards plagued early radiography

A

Excessive radiation exposure

Electric shock

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5
Q

A component of the xray imaging system rarely seen by radiologic technologist

A

Xray tube

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6
Q

Xray tube is contained in

A

Protective housing

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7
Q

Modern xray tube is a

A

Vacuum tube

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8
Q

Xray tube contains 2 electrodes:

A

Anode

Cathode

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9
Q

Size of the xray tube

A

30-50 cm long

20 cm in diameter

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10
Q

Two principal parts of the xray tube:

A

Anode (rotating)

Cathode

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11
Q

Tube that has two electrodes

A

Diode

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12
Q

Self rectification highest limits are about

A

30 mA at 90 kVp

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13
Q

External structure of the xray tube:

A

Support structure
Protective housing
Glass or metal enclosure

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14
Q

Internal structure:

A

Anode and cathode

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15
Q

3 main methods of xray tube support

A

Ceiling support system
Floor to ceiling support system
C-arm support system

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16
Q

The most frequently used

Consist of two perpendicular sets of ceiling mounted rails

A

Ceiling support system

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17
Q

Has a single column w/ rollers at each end (attached to the ceiling and to the floor)

A

Floor to ceiling support system

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18
Q

Ceiling mounted and provide very flexible positioning

A

C-arm support system

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19
Q

Tube is housed in a _________protective housing

A

Lead line metal

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20
Q

Generated isotropically or in all directions

A

Xray photons

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21
Q

It limits the beam to window

A

Housing

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22
Q

Controls leakage , scattered radiation , isolates the high v and provides a mean to cool the tube

A

Housing

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23
Q

Photons that escape from the housing except at the port

A

Leakage radiation

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24
Q

Leakage radiation must not exceed

A

100 mR /hr at 1 meter

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25
Q

Provides mechanical support and protection

A

Housing

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26
Q

Provides more insulation and thermal cushion

A

Oil

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27
Q

To protects againts electrical shock , the housing incorporates

A

High voltage receptacles

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28
Q

Maintains the vacuum inside the tube

A

Glass enclosure

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29
Q

Glass enclosure is made of ______ to enable to withstand the heat generated

A

Pyrex

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30
Q

It is where useful beam is emitted

A

Window

31
Q

Size of the window

A

5cm ^2

32
Q

Allows more efficient production of xray and tube life

A

Vacuum

33
Q

With the presence of air:

A

Electron flow is reduced
Few xrays
More heat

34
Q

Maintain a constant electric potential between the electrons of current and enclosure

A

Metal enclosure

35
Q

Negative side of the tube

A

Cathode

36
Q

2 parts of the cathode

A

Filaments

Focusing cup

37
Q

Emits electrons when heated

A

Filament

38
Q

Filaments are made up of

A

Thoriated tungsten

39
Q

Provides higher thermionic emission and melting point is 3410 c

A

Tungsten

40
Q

Most rotating anode xray tubes have

A

Two filaments

41
Q

The most common tube failure

A

Tungsten vaporization

42
Q

Designed to house the filament

Metal shroud that surrounds the filament

A

Focusing cup

43
Q

Has a negative charge to confine electron beam to small area of anode

A

Focusing cup

44
Q

Effectiveness of focusing cup

A

Size and shape
Charge
Filament size and shape
Position of filament

45
Q

Emission of electrons fr heated surface

A

Thermionic emission / thermal electron emission

46
Q

The process which charged carriers move over a surface by the induction of heat

A

Thermionic emission

47
Q

Formation of electron cloud near the filament

A

Space charge

48
Q

More electrons build up the filament, negative charges begin to oppose the emission

A

Space charge effect

49
Q

As kVp increases , great percentage of the thermionically emitted electrons are driven towards anode

A

Saturation current

50
Q

Parts of the anode

A

Anode target
Stator
Rotor

51
Q

Positive side of the tube

A

Anode

52
Q

Functions of the anode

A

Electrical conductor
Mechanical support
Thermal dissipator

53
Q

Anode materials

A

Copper
Molybdenum
Graphite

54
Q

Conducts electricity and radiates heat and contains target

A

Anode

55
Q

2 types of anode

A

Stationary

Rotating

56
Q

Used in dental xrays , does not require high tube current

A

Stationary anode xray tube

57
Q

General purpose xray tubes , capable to produce high tube current

A

Rotating anode xray tube

58
Q

Does not move when an exposure occurs

A

Stationary anode

59
Q

Rotates during exposure

A

Rotating anode

60
Q

Made of graphite for solid base

A

Base

61
Q

Made of tungsten - rhenium alloy

A

Target

62
Q

Parts holding target is made of

A

Molybdenum

63
Q

Area of the anode struck by electrins from cathode

A

Target

64
Q

Target material on stationary

A

Tungsten alloy in copper anode

65
Q

Target material on rotating

A

Tungsten w/ rhenium

66
Q

High capacity xray tubes have ________ under the tungsten target making it lighter

A

Molybdenum or graphite layer

67
Q

Why tungsten is the material of choice

A

Atomic number
Thermal conductivity
High melting point

68
Q

Measure of ability of a substance to conduct heat

A

Thermal conductivity

69
Q

Melting point of tungsten

A

3422 c / 6192 F

70
Q

Melting point of copper

A

1083 c / 1981.4 F

71
Q

Leads to creation of small holes in the metal

A

Pitting corrosion

72
Q

Actual target area of stationary

A

4mm2

73
Q

Target area of rotating

A

1,760 mm2

74
Q

Shaft between the anode and the rotor

A

Anode stem

75
Q

Stem is made up of _____ because of poor conductor of heat

A

Molybdenum

Radphy 2 (8 decks)

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