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RT 209 > 5. X-ray Machine and Tube > Flashcards

5. X-ray Machine and Tube Flashcards

1
Q

3 MAIN COMPONENTS OF AN X-RAY IMAGING SYSTEM

A
  • X-ray tube
  • Operating console
  • High voltage generator
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2
Q

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

A

X-ray Tube

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3
Q

EXTERNAL COMPONENTS

A
  • Support structure
  • Protective housing
  • Glass or metal enclosure
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4
Q

consists of two perpendicular sets of ceiling-mounted rails

A

Ceiling Support System

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5
Q

has a single column with rollers at each end

A

Floor to Ceiling Support System

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6
Q

the image receptor is attach to the end of the C-arm from the x-ray tube

A

C-arm Support System

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7
Q

guards against excessive radiation exposure and electrical shock

A

Protective Housing

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8
Q

is made up of pyrex to withstand the tremendous heat generated

A

Glass or Metal Envelope

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9
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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10
Q

X-rays emitted through the window is called the

A

useful beam

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11
Q

X-rays that escaped through the tube housing are called

A

leakage radiation

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12
Q

Leakage radiation should not exceed ______ when operated at maximum condition

A

100 mR/hr at 1 m

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13
Q

INTERNAL COMPONENTS

A
  • Cathode

* Anode

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14
Q

is the negative side of the x-ray tube and had two primary parts: a filament and a focusing cup

A

Cathode

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15
Q

usually approximately 2mm in diameter and 1 or 2 cm long

A

Filament

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16
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

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17
Q

Filaments are usually made of

A

thoriated tungsten

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18
Q

Filaments are usually made of thoriated tungsten because

A
  • Tungsten have high melting point (3410 C)
  • Does not vaporize easily
  • Addition of 1% to 2% thorium to tungsten increases the efficiency of thermionic emission
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19
Q

where the filaments are embedded

A

Focusing Cup

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20
Q

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

A

small focal spot

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21
Q

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

A

large focal spot

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22
Q

is the positive side of the x-ray tube

A

Anode

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23
Q

it conducts electricity and radiates heat and contains the target

A

Anode

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24
Q

FUNCTIONS OF ANODE ASSEMBLY

A
  • Electrical conductor
  • Mechanical support
  • Thermal dissipator
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25
Q

area of the anode struck by the electrons from the cathode

A

Target

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26
Q

TYPES OF ANODE

A
  • Stationary anode

* Rotating anode

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27
Q

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

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28
Q

capable of producing high intensity x-ray beam

A

Rotating Anode

29
Q

heat capacity can be further improved by increasing the speed of anode rotation

A

Rotating Anode

30
Q

Rotating Anode rotates

A

3400 rpm and 10,000 rpm

31
Q

the target is consists of tungsten alloy embedded in a copper anode

A

stationary anode tubes

32
Q

stationary anode tubes size

A

About 4 mm^2

33
Q

the entire rotating disc is the target

A

rotating anode tubes

34
Q

rotating anode tubes size

A

About 3159 mm^2

35
Q

Tungsten is the material of choice for the target for general radiography for 3 main reasons

A
  • Atomic number
  • Thermal conductivity
  • High melting point
36
Q

specialty x-ray tubes for mammography have ______ targets principally because of their low atomic number and low K characteristics x-ray energy

A

molybdenum or rhodium

37
Q

is powered by an electromagnetic induction motor

A

rotating anode

38
Q

an induction motor is consist of 2 parts:

A

the stator and the rotor

39
Q

is the actual x-ray source

A

Focal Spot

40
Q

results in an effective focal spot size much less than the actual focal spot size

A

Line-Focus Principle (Goetze Principle)

41
Q

diagnostic x-ray tubes have target angles that vary from approximately ____ degrees

A

5 to 20

42
Q

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

A

Heel Effect

43
Q

the smaller the anode angle, the ____ is the heel effect

A

larger

44
Q

greater anode angle _____ useful beam

A

wider

45
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

46
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
47
Q

3 WAYS TO DISSIPATE HEAT

A
  • Radiation
  • Conduction
  • Convection
48
Q

CAUSES OF X-RAY TUBE FAILURE

A
  • Vaporized tungsten
  • Rotor bearings breakage
  • Anode pitting
  • Cracked anode
49
Q

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

A
  • Radiographic rating chart
  • Anode cooling chart
  • Housing cooling chart
50
Q

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

A

Heat Units (HU)

51
Q

One heat unit is equal to the product of

A

1 kVp, 1 mA, and 1s

52
Q

SINGLE-PHASE Heat Unit

A

HU = kVp x mA x s

53
Q

THREE-PHASE/HIGH-FREQUENCY Heat Units

A

HU = 1.4 x kVp x mA x s

54
Q

1 HU =

A

1 HU = 1.4 J

55
Q

1 J =

A

1 J = 0.7 HU

56
Q

Radiographic x-ray tube housings usually have ______ heat capacities in the range of several million heat units

A

maximum

57
Q

Complete cooling after maximum heat capacity requires from

A

1 to 2 hours

58
Q

transfers heat from focal spot track to anode body

A

Conduction

59
Q

transfers heat from focal spot track to tube housing

A

Radiation

60
Q

transfers heat from tube housing to the atmosphere

A

Convection

61
Q

atomic number of Niobium

A

41

62
Q

atomic number of Silicon

A

14

63
Q

atomic number of Germanium

A

32

64
Q

atomic number of Titanium

A

22

65
Q

atomic number of Molybdenum

A

42

66
Q

atomic number of Rhodium

A

45

67
Q

k-shell binding energy of Molybdenum

A

19 keV

68
Q

k-shell binding energy of Rhodium

A

23 keV

RT 209 (11 decks)

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