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RADT Unit 1 > X-ray Tube Construction > Flashcards

X-ray Tube Construction Flashcards

1
Q

Milliampere (mA) and Time (s) controls?

A

Quantity and Density

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2
Q

How does Milliampere (mA) control quantity?

A

Amount of electrons emitted at the filament by process of thermionic emission

  • more # of electrons = more # of x-rays being emitted
  • less # of electrons=less # of x-rays being emitted
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3
Q

How does Time (s) control quantity?

A

determines length of time electrons are allowed to flow from cathode to anode

  • more time -> more electrons> more x-ray
  • less time-> less electrons-> less x-ray
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4
Q

The combination of Milliampere (mA) and Time (s) is?

A

mAs (milliampere seconds)
-treated as one unit

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5
Q

Kilovoltage (kV) controls?

A
  • Quality
  • Penetrating power
  • Energy
  • Density and Contrast
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6
Q

What is Contrast?

A

difference b/w black and white

ex)
- The higher the kV the darker the image
-The lower the kV the lighter the image

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7
Q

What is Density?

A

Overall degree of darkness

ex)
- too strong of kV the blacker the image will get
-too light of kV the whiter the image

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8
Q

There are three different types of External and Mechanical Support in a X-ray Room Structure. What are they?

A
  1. Ceiling
  2. Floor-to Ceiling
  3. C arm
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9
Q

Ceiling support

A
  • most common
  • freely moves in all directions : transverse
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10
Q

Floor-to- Ceiling support

A
  • Multi-directional
  • Requires effort to move
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11
Q

C arm Support

A
  • Nearly limitless in tube position
  • Robotic and fluid in motion
  • Angiography
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12
Q

Protective Housing is considered to be_____?

A

Isotropic

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13
Q

The useful beam-emitted through the window of protective housing is also called?

A

Primary beam

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14
Q

Anything else which escapes the protective housing is called?

A

Leakage radiation or Secondary beam

-non-diagnostic
- unnecessary exposure to both patient and technologist

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15
Q

Protective housing is lined with what material?

A

Lead

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16
Q

Why is protective housing lined with lead? and why is protective housing important?

A
  1. reduce leakage radiation (<100 mR/hr @1meter)
    2.
    -Provides mechanical support
    - Protects from damage caused by rough handling
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17
Q

Protective housing contains ________ to insulate from shock and dissipate heat.

A

Oil

18
Q

Electron to x-ray efficiency is __%

A

1%

-99% is heat

19
Q

What is Pyrex glass and why is it important?

A
  • withstands large amounts of heat
  • Vacuum
    • more efficient x-ray production
    • Longer tube life
20
Q

What is a Cathode ?

A

Negative Electrode Filament
-(2) coils of wire (toaster vs x-ray filament)

21
Q

What is Dual Focus?

A

Refers to Large FSS and Small FSS

22
Q

What does FSS stand for?

A

Focal Spot Size

23
Q

Dual Focus Cathode contains 2 filaments. What are they?

A
  1. Small Filament
  2. Large Filament
24
Q

Small focal spot size filament uses ____mA or less

A

200

-provides better detail
- best for small body parts

25
Q

Large focal spot size filament uses _____mA or more

A

300
-larger body parts
-can withstand more heat

26
Q

What is a Focusing Cup?

A

Negative charge that surrounds the filament on the cathode

-confines electron beam to small area of anode

27
Q

What is Thermionic Emission?

A

When electrons are boiled off

28
Q

What is the space-charge effect?

A

Prevents subsequent electrons from being boiled off due to electrostatic repulsion (same charges repel)-Coulomb’s Law

29
Q

What is an Anode?

A

Positive electron

30
Q

What is a stationary Anode?

A
  • High tube current and power not required
  • Used in dental offices, clinics, portables, simple x-ray units
  • Has a copper Anode and Tungsten Target
31
Q

What is a Tungsten Target?

A
  • In the middle of copper anode
  • Most important primary material
32
Q

What is a con to a stationary anode?

A

Pitting can occur

33
Q

What is Pitting?

A

wear and tear of the Tungsten Target which can also lead to tube failure

34
Q

What does a Rotating Anode help do?

A

x-ray tubes capable of producing high-intensity x-ray beams in shorter time periods
-Has Copper, Molybdenum, Rotating Tungsten Target, Target Track

35
Q

The rotating anode has________ to ________ RPM?

A

3,600 to 10,000 RPM (Rotations Per Minute)

36
Q

Why is a Rotating Anode better compared to a Stationary Anode?

A
  • Better for heat dissipation
  • Higher tube currents with shorter exposure time (more efficient)
  • Increased heat loading abilities
37
Q

What is a Target (track)?

A

Area of disc that the electrons strike, and are converted into x-rays

38
Q

Disc is composed of 3 layers. What are they?

A
  1. Tungsten/rhenium
  2. Molybdenum
  3. Graphite
39
Q

Why is Tungsten used?

A
  • High atomic #(74)
  • Higher Efficiency
  • Thermal Conductivity
  • Better at heat dissipation
  • High Melting Point
  • Minimize occurences of pitting
40
Q

What is the high melting point of Tungsten?

A

3410 °C (6170 °F)

RADT Unit 1 (7 decks)

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