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RT: 34 > Tube rating charts > Flashcards

Tube rating charts Flashcards

1
Q

Name the external components of an x-ray tube

A
  1. Ceiling Support system
  2. Floor to ceiling support system
  3. C-arm support system
  4. Protective housing
  5. Glass/metal enclosure
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2
Q

Which x-ray unit is most common

A

The ceiling support system

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3
Q

Leakage radiation must be no more than ____>

A

1 mGy/hr @ 1 meter from the source

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4
Q

What is the purpose of protective housing

A

guards against excessive radiation exposure & electric shock

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5
Q

What is the tube ( anode & cathode) enclosed by?

A

Glass vacuum

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6
Q

What surrounds the glass vacuum x-ray tube

A

metal housing

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7
Q

What happens when the area inside the glass tube housing is not a vacuum?

A

the electrons collide with other atoms when traveling from the cathode to the anode and thus, creates less x-rays or lower energy xrays, AND decreases the efficiency of the tube.

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8
Q

What are the internal components of the x-ray tube

A

Cathode and Anode

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9
Q

Where does thermionic emission take place

A

in the cathode side of the tube

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10
Q

What does the cathode consists of

A
  • negative side of tube*
    Contains:
    -Filaments
    -Focusing cup
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11
Q

What is the positive side of the x-ray tube

A

anode

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12
Q

What are the 2 types of anodes

A
  1. Rotating
    (used in x-ray)
    2.Stationary
    (used in dental)
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13
Q

Why are rotating anodes used in general x-ray

A

because they can produce high intensity x-ray beam in a short amount of time

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14
Q

What is the anode made of

A
  1. Tungsten
  2. Molybdenum
  3. Rhodium
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15
Q

Why is tungsten used in the anode

A
  1. High atomic #
  2. Thermal conductivity
  3. High melting point
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16
Q

What is the element for:

  1. Tungsten
  2. Molybdenum
  3. Rhodium
A
  1. W
  2. Mo
  3. Rh
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17
Q

Fixed electromagnets of the tube are called

A

Stators

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18
Q

What is the purpose induction motor of anode

A

It is an electric motor where magnetic field is supplied to fixed electromagnets called stators to rotate the rotor of the anode

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19
Q

Electric motor where magnetic field is supplied to fixed electromagnets called stators to rotate the rotor of the anode

A

Induction motor of anode

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20
Q

What is the line focus principal

A

A designed added to x-ray tube targets that allow for larger heating areas while a small focal spot is maintained

21
Q

How is focal spot size controlled

A

Controlled by angle of the target

22
Q

Effective focal spot size is _____ than the actual spot size

A

less than the actual spot size

23
Q

The larger the target angle the ____ focal spot size

A

larger

24
Q

How does a change in focal spot affect the anode

A

the tube changes the location of the anode

small= towards center of anode

Large= edge of anode

25
Q

What is an undesirable result of line focus principal

A

unequal radiation intensity across the anode & the cathode

26
Q

Intensity is greater on the ___ side, as a result of electrons hitting the target at different depths

A

Cathode

27
Q

The ___________ the anode angle, the larger the heel effect

A

smaller

28
Q

What are some of the things we use to reduce the anode heel-effect

A

Filters

29
Q

What are 3 ways that heat is dissipated from the x-ray tube

A
  1. Radiation
  2. Conduction
  3. Convection
30
Q

The transfer of heat by the emission of infrared radiation is _____

A

Radiation

31
Q

The transfer of energy from one area of an object to another is _____

A

Conduction

32
Q

The transfer of heat by a movement of a heated substance from one place to another

A

Convection

33
Q

Excessive heat results in ____

A

reduced x-ray tube life

34
Q

What do we do as technologists to prolong tube life?

A

Tube warm up

35
Q

Name factors that prolong tube life

A
  1. Tube warm up
  2. Low techniques
  3. Faster IR’s/screens
36
Q

Maximum radiographic techniques should never be applied to a cold anode. Why?

A

anode pitting occurs
= this means that the tungsten removed during pitting get deposited in the glass envelope of tube housing
which causes tube arching

37
Q

What are the 3 types of tube failure

A
  1. excessive heat during single exposure
  2. maintaining anode at elevated temperatures
  3. Filament
38
Q

What does excessive heat during exposure cause?

A

causes anode to crack which is then unstable during rotation

39
Q

Name the 3 types of rating charts

A
  1. Radiographic` tube rating charts
  2. Anode cooling chart
  3. Housing cooling chart
40
Q

Which rating chart is most important and why

A

Radiographic rating chart because it details which techniques are safe to use and which are not for tube operation

41
Q

Phase refers to what type of generator the tube is powered by….
What are some types of generators?

A 
single phase
three phase
high frequency
half wave
full wave
42
Q

Large effective focal spot has which anode angle?

A

Large

43
Q

How is thermal energy in x-ray applications measured in

A

Heat Units (HU)
or
Joules (J)

44
Q

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

A

HU

Heat units

45
Q

1 heat unit is equal to

___ kVp
___mA
___ s

A

1 kVp
1 mA
1 s

46
Q

How would you find a HU for single phase

A

kVp x mA x time

47
Q

How would you find HU for High frequency circuit

A

kVp x mA x time x 1.4

48
Q

The ____ will overheat long before the tube housing will

A

anode

49
Q

Why does the anode overheat before the tube housing?

A
  1. the anode is being directly bombarded with electrons, where the tube housing is indirectly bombarded
    AND
  2. the anode is made of tungsten where the tube housing is made of an insulator material)

RT: 34 (8 decks)

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