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Radiologic Exposures > Xray Tube > Flashcards

Xray Tube Flashcards

1
Q

What is part of the cathode ?

A

Filament and focusing cup

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2
Q

What charge is the cathode

A

Negative

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3
Q

What charge is the anode

A

Positive

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4
Q

What kind of material is the filament made of ?

A

Thoriated Tungsten

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5
Q

What material is the focusing cup made of

A

Nickel

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6
Q

Target

A

May also be called the focal point, focal spot, or the focal track

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7
Q

Tube housing

A

Protects against leakage radiation and electric shock

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8
Q

Thermionic Emission

A

The process of boiling off electrons and produces a cloud of electrons by heating the filament

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9
Q

Space charge effect

A

Occurs when no more electrons can be boiled off the filament

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10
Q

Three components of anode.

A

Anode, stator and rotor

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11
Q

Is the primary thermal conductor of the tube

A

Anode

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12
Q

Two types of anodes

A

Rotating and stationary

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13
Q

Portion of the anode struck by electrons

A

Target

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14
Q

What is the anode made up of

A

Tungsten rhenium alloys

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15
Q

What does it mean to have two filaments

A

Dual focus tube

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16
Q

Why does the X-ray tube need to be warmed up

A

Prevent cracking and maintain vacuum

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17
Q

Purpose of rotating anode

A

Promote greater heat dissipation

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18
Q

What determines the number of electrons boiled off

A

mA

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19
Q

Anode heel effect

A

Absorption of X-rays produces in the tube by the anode, causes uneven distribution of X-ray intensity between the cathode and anode, more intensity on cathode side (fat cat)

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20
Q

Project area of X-ray beam

A

Effective focal spot

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21
Q

Cardinal rules of Radiationg Protection developed to prevent radiation injury

A

Time, distance, shielding

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22
Q

Why is tungsten used

A

High melting point and Difficult to vaporize

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23
Q

Atomic number of tungsten rhenium alloy

A

74

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24
Q

Who was the first fatality from X-rays in 1904

A

Clarence Dally

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25
Q

Area where electrons strike the anode

A

Focal spot

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26
Q

Who devised a fluoroscope

A

Thomas Edison

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27
Q

Who improved the crooked tube

A

William Coolidge

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28
Q

What was the first ever xray

A

Roentgens wife’s hand

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29
Q

Leakage radiation limit

A

100 milliroentgens per hour at 1 meter

30
Q

When was X-rays discovered

A

Nov 8, 1895

31
Q

Physical area of the focal track being hit by the electrons.

A

Actual focal spot

32
Q

What is the environment inside the X-ray tube once all air has been removed

A

Vacuum

33
Q

Who discovered X-rays

A

Wilhelm Conrad roentgen

34
Q

Necessary qualities of the anode

A

High atomic number, high melting point, and high heat conduction ability

35
Q

Heat tolerant Pyrex glass or metal

A

Envelope

36
Q

What do electrons become when they hit the anode

A

Photons

37
Q

What two things control the size of the effective focal spot

A

Size of the actual focal spot and anode target angle

38
Q

What is the line focus principle

A

Spreads heat over a greater area of the anode and allows the effective focal spot to be smaller than the actual focal spot

39
Q

What is the purpose of the glass envelope

A

Absorbs X-rays and ensure a vacuum

40
Q

Purpose of the focusing cup

A

To group the electrons for their passage to the anode

41
Q

A molybdenum shaft is used to connect the anode to the rotor because

A

It is a less dense metal with a high melting point that helps anode to spin faster

42
Q

Purpose of the fan in the tube housing is to

A

Promote heat dissipation

43
Q

Average anode rotation speeds in diagnostic ray tubes are in the ranges of :

A

3,000-10,000

44
Q

These are all apart of production of X-rays

A

Electrons, target, high voltage , and vacuum

45
Q

Is made of molybdenum and connects the anode to the rotor

A

Stem

46
Q

What is the X-ray efficiency

A

1% X-ray , 99% heat

47
Q

The only thing located outside of the envelope that consists of copper windings

A

Stator

48
Q

Made of a copper cylinder in the step of the X-ray tube and is support by the high strength ball bearings

A

Rotor

49
Q

What are two types of cathode failures

A

Tube arcing and filament breakage

50
Q

What is it called when they are holes on the focal track

A

“Pitting”

51
Q

What is anode layering

A

Assists with heat loading and increases X-ray tube thermal capacity. It is backed with molybdenum or graphite

52
Q

What does the protective housing consist of

A

Metallic , supports X-ray tube, controls leakage and scatter radiation, provide mechanisms to cool tube

53
Q

How can we extend the tube life

A
  • tube warm up
  • avoid frequent “boosting”
    -use low mA when possible
  • use low speed rotation when possible
  • follow rotating charts
  • avoid rough handling
  • listen to unusual sounds
54
Q

What is off focus radiation

A

Undesirable part of the beam , not hitting anode, low energy and no diagnostic value, produces “ghosting”

55
Q

What does X-ray stand for

A

The x in X-ray means unknown

56
Q

What is the divergence of the beam

A

Energy that is coming out and what’s interacting with the patient

57
Q

True or false
X-rays are invisible

A

True

58
Q

True or false
X-rays can travel around corners

A

False

59
Q

True or false
Taking X-rays is a safe profession

A

True

60
Q

True or false
Radiation can cause harm to your body

A

True

61
Q

Sequence of taking X-rays

A
  1. Current runs through the filament circuit
  2. Filament gets hot
  3. Filament glows
  4. Filament boils of electrons
  5. Electrons form a space cloud
  6. Electrons are repelled from the focusing cup
  7. Electrons are attracted by the anode
  8. Electrons move over to the anode
  9. Electrons slam into the anode at the target
  10. Electrons lose energy
  11. Light, heat and X-rays are produced
  12. Focal spot if formed
  13. X-rays are emitted isotropically
  14. X-rays are absorbed by the glass and metal housing
62
Q

True or false
X-rays are electrically neutral

A

True

63
Q

True or false
X-rays have mass

A

False (X-rays have no mass)

64
Q

True or false
X-rays can be focused

A

False - can’t be focused or refracted

65
Q

True or false X-rays travel in straight lines

A

True

66
Q

ways to avoid dangers of radiation

A
  • never stand in primary beam
    -collomating as small as you can
  • never hold patient
    -lead protection
  • radiation dose monitored through use of dosimeter
67
Q

what type of body parts would the small filament focus on

A

small focusing body part (less heat)

68
Q

what type of body parts would the large filament focus on

A

large focusing body parts (more heat)

69
Q

what does the filament produce

A

filament produces electrons to produce image

70
Q

what does the filament length and width impact

A

recorded detail or special resolution

71
Q

Typically controlled by the xray circuitry and wont go hight that what is already set

A

Saturation Current

Radiologic Exposures (11 decks)

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