X-Ray Units Flashcards

1
Q

What is the purpose of the lead shield in X-ray units?

A

To prevent electrons from traveling outside of it

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2
Q

What is the purpose of the oil bath?

A

To absorb heat

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3
Q

What is the purpose of copper?

A

To absorb heat

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4
Q

What are the two components of the cathode?

A

filament

focusing cup

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5
Q

What are the two desired properties of the cathode?

A

electrical conductivity

high vapor pressure

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6
Q

How are electrons produced in the cathode?

A

By thermionic emission

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7
Q

The process by which the cathode filament is heated, the electrons are boiled off and the electrons are then accelerated toward a tungsten target is called ______.

A

thermionic emission

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8
Q

What is the sequence of thermionic emission and at what point are X-rays generated?

A
  1. Cathode
  2. Electrons
  3. Anode (X-rays generated here)
  4. X-rays
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9
Q

What are the three desired properties of the anode?

A

electrical conductivity
high melting point
high atomic number; i.e., Tungsten

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10
Q

To take advantage of a small focal spot while distributing the electrons over a larger area of the target, the target is placed at an angle to the electron beam. This is called ________.

A

line focus principle

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11
Q

True or False? The angle of the target to the central ray of the x-ray beam has a strong influence on the apparent size of the focal spot.

A

True

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12
Q

When are rotating anode tubes used?

A

When heavy use is demanded such as in hospitals

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13
Q

How are current and voltage related?

A

They are inversely related

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14
Q

The movement of electrons is known as _____.

A

electrical current

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15
Q

The rate of current is the number of electrons moving past a point in a second and is measured in ______.

A

amperes

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16
Q

The flow of electrons through the x-ray tube is referred to as _________.

A

tube current

17
Q

Tube current is measured in _____.

A

milliamperes mA

18
Q

The energy of the electrons is the _____.

19
Q

Voltage is measured in ______ and in dental radiography in _______.

A

volts, kilovolts kV

20
Q

______ translates to maximum energy of x-ray photons in a beam.

A

Peak kV or kVp

21
Q

What is the potential difference between the anode and the cathode?

A

tube voltage

22
Q

Tube voltage is measured in _____.

A

kVp or peak kilovoltage

23
Q

What is the normal voltage for dental radiography?

24
Q

What are the two primary functions of the power supply of an x-ray machine?

A
  • provide a low voltage current to heat the x-ray tube filament by use of a step-down transformer
  • generate a high potential difference between the anode and cathode by use of a high-voltage step up transformer
25
What reduces the voltage at the cathode from 110 to 10 volts which in turn requires an increase in the amperage of the filament circuit by a factor of ten from about 500mA to 5000 mA or 5 Amps?
step-down transformer
26
What transforms the 110 volts from the wall outlet to 65,000 to 70,000 volts which in turn requires a reduction in the amperage from 500mA to 5 to 7 Amps due to increased voltage?
Step-up transformer
27
What are the three purpose of recitification?
- increased efficiency - shortened exposure time - more reliable radiation output
28
What are the four purposes of X-ray generation?
- increased efficiency - increased mean of energy of beam - shortened exposure times - more reliable radiation output
29
_____ relates to the frequency with which successive exposures can be made.
Duty cycle
30
What are the desired characteristics of x-ray tube housing?
- x-ray absorptive | - heat conductive