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Image Prod & Eval > Chapter 10 - midterm > Flashcards

Chapter 10 - midterm Flashcards

1
Q

What type of waves are x-rays?

A

Electromagnetic waves

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2
Q

How are x-rays created?

A

Electrons must be accelerated with thousands of volts towards the anode

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3
Q

What is the kinetic energy formula?

A

KE=1/2 mv^2

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4
Q

In what distance do electrons reach the speed of light?

A

In less than an inch between the filament and anode disc

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5
Q

What are the two types of interactions that electrons have within the tube?

A
  • Bremsstrahlung
  • Characteristic
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6
Q

Which of the two electron interactions in the tube produces the majority of x-rays?

A

Bremmstrahlung

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7
Q

How does Bremsstrahlung work?

A

An incoming electron passes near the atomic nucleus, where the strong electric field of the nucleus causes the electron to break down and release an x-ray photon

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8
Q

What are x-rays produced as part of Bremsstrahlung interactions called?

A

Bremmstrahlung

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9
Q

What does Strahlung mean?

A

Radiation

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10
Q

What does Bremse mean?

A

Brake

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11
Q

What is the probability a projectile electron will pass within the inner sphere of an atom?

A

2%

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12
Q

What is the probability a projectile electron will pass within the outer sphere of an atom?

A

20%

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13
Q

What is the result of an electron that passing through the inner sphere of an atom?

A

An x-ray photon with higher emitted energy

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14
Q

How does the process work to create higher energy electrons from inner sphere of the atoms?

A

The closer an electron gets to a nucleus, the greater the deceleration occurs. With greater deceleration the more the electron deviates from its original direction and more kinetic energy is lost.

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15
Q

What effect does Bremsstrahlung have on the energy levels of x-ray beam?

A

It produces a beam with a wide range of energies

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16
Q

What does the wide range of energy contribute to in diagnostic imaging?

A

Contributes to the different absorption of x-rays within patient tissues

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17
Q

What does differential absorption provide?

A

The subject contrast to the beam to make imaging possible

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18
Q

What would be the result if all x-rays were the same energy?

A

Silhouette images that stop at deep tissue

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19
Q

What is the function of filtration within an x-ray tube?

A

Filters out low energy photons

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20
Q

What are examples of filtration in a tube?

A
  • Sheet of Aluminum or Copper
  • Inherent filtration (collimator mirror, x-ray tube window)
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21
Q

What is the aluminum equivalent of filtration?

A

2.5 mm Al/equivalent

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22
Q

What is added filtration designed to do?

A

Reduce patient exposure to photons of long wavelengths (low energy photons)

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23
Q

What happens to the average beam energy after filtration?

A

The average beam energy will go up but the overall intensity goes down

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24
Q

What is the average energy of a x-ray beam after Bremsstrahlung distribution and filtration?

A

1/3 of what is set on the x-ray console when using single phase generator

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25
Q

What is a rule of thumb for the energy levels of a photon created via Bremsstrahlung?

A

The energy of the Photons cannot be more than the original kVp set

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26
Q

When does characteristic radiation occur?

A

When an incoming electron passes near an orbital electron, displaces it and leaves a vacancy in a shell and cascading effect occurs until all vacancies are filled

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27
Q

What is the charge of the atom after characteristic interaction?

A

Atom has an overall positive charge

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28
Q

What does the atom seek to do after the electron is displaced via characteristic radiation?

A

It seeks to return its charge to ground state which causes an outer orbital electron to fall down

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29
Q

What happens when the electron from the outer shell falls into the inner shell?

A

There is a change in potential energy which causes an x-ray photon to be discharged

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30
Q

What is the x-ray called when emitted via characteristic radiation?

A

Characteristic x-ray

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31
Q

What is the energy of characteristic radiation dependent on?

A

The energy of the electron shell where the originally bound electron was knocked out and the binding energy from the shell where the electron drops down from

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32
Q

What are the kV levels of electrons falling from outer shells into the K shell for Tungsten?

A

57, 66, 68 and 69 kV

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33
Q

How is emitted kV energy calculated in characteristic interactions?

A

Inner shell energy - outer shell energy
Ex: 69-.01 = 69, 69-1=68

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34
Q

What percent of projectile energy from incoming electrons is turned into x-ray photons?

A

.5%

35
Q

What makes up the remaining 99.5%?

A

Heat through a process called excitation

36
Q

What is the process of excitation?

A

When electrons in the atom are raised to a higher energy state but not knocked out of their shells

37
Q

What happens when the electrons fall back into place after excitation?

A

They release infrared radiation and light which causes vibration and heat to occur

38
Q

How does atomic number affect the efficiency of x-ray beams produced?

A

The higher the atomic number of the anode, the more efficient and more x-rays are produced

39
Q

How do gold(AU) and tungsten (W) compare in atomic # and efficiency?

A

Gold has a Z# of 79 and Tungsten has a Z# of 74, making gold more efficient

40
Q

Why is gold not a good metal for x-ray production despite its high Z#?

A

It is expensive and has a much lower melting point than tungsten

41
Q

What is the melting point of gold?

A

1948 F

42
Q

What is the melting point of Tungsten?

A

6192 F

43
Q

What affects the efficiency of x-ray production?

A

The target material of the anode

44
Q

What governs the intensity (quantity) of the x-ray beam?

A

mA and T (seconds)

45
Q

What is the product of mA and T called?

A

mAs

46
Q

What is the relationship between mAs and quantity of photon creation?

A

Directly proportional as mAs increase, so does the number of photons

47
Q

How is mAs related to exposure/dose?

A

Also directly proportional, as mAs increases so does exposure/dose

48
Q

What does kVp do to the electrons from the cathode?

A

They give the electrons the push to move the electrons to the target

49
Q

What is the push of the electrons from the cathode to the target called?

A

Potential difference

50
Q

What does increased kVp increase in tissues?

A

Increases penetration

51
Q

How does an increase in kVp affect the movement of electrons?

A

When a higher kVp is set the electrons move at a higher speed, which produces a higher energy x-ray beam

52
Q

How does a decrease in kVp affect the movement of electrons?

A

When a lower kVp is set the electrons move at a lower speed, which produces a lower energy x-ray beam

53
Q

What affect does increased kVp have on the beam?

A

It increases the quantity (# of photons) and the quality of the beam (energy)

54
Q

What is the only prime exposure variable that can change the energy of the xray beam?

A

kVp

55
Q

What is the mathematical relationship between kVp and keV?

A

100 kVp = 100 keV

56
Q

What does keV measure?

A

The energy of x-ray photons

57
Q

What is the mathematical relationship between kVp and intensity?

A

Intensity 1/Intensity 2 = kVp1^2/kVp2^2

58
Q

What other aspects of exposure does increase kVP affect?

A

Dose, Receptor Exposure, Image Contrast

59
Q

What relationship does kVp have with dose?

A

Increased kVp increases dose proportionately

60
Q

What is the relationship between kVp and Exposure?

A

+15% kVp = 2x Exposure

61
Q

What is the relationship between kVp and image contrast?

A

Increase kVp, decreases image contrast

62
Q

If a technologist wants to increase quantity what exposure factor should be increased?

A

Kvp vs mAs

63
Q

Why would increasing kVp over mAs be better for the patient?

A

It saves the patient dose due to reduced photoelectric effect

64
Q

How does the voltage of a machine affect the beam intensity?

A

Higher voltage applied to the tube, more efficiently increases the intensity of the beam

65
Q

How do single-phase and three-phase machines compare?

A

Three-phase machines keep their x-ray production at its surge state, which produces more beams at higher average energies

66
Q

What affect does a higher power machine have on the xray beam?

A

Increases both quantity and quality, which allows the radiographer to use lower kVp/mAs to achieve exposures

67
Q

How does the size of a wavelength affect penetration?

A

The shorter the wavelength, the more penetrating it is and worse for you

68
Q

How does kV affect wavelength size?

A

Higher the kv the shorter the wavelength

69
Q

How does frequency change when moving from left to right on EM Spectrum?

A

Frequency increases as wavelengths get smaller/stronger

70
Q

What electromagnetic waves are visible?

A

Light is visible

71
Q

What electromagnetic waves are invisible?

A

X-rays, gamma rays, radio waves

72
Q

How is energy related to wavelength?

A

The shorter the wavelength the higher the energy

73
Q

How are X-rays produced?

A

MAs is applied to the filament, which heats up and produces a cloud of electrons that boil off by thermionic emission. KV is then added to push the electrons to the target which they hit (focal spot).

74
Q

At what kVp does Bremmstrahlung occur?

A

Above 70 kVP

75
Q

Is there a physical interaction in Bremsstrahlung?

A

No physical interaction

76
Q

What is the 2.5 mm AL/equivalent made up of?

A

The inherent filtration + added filtration

77
Q

What is the atomic number of molybedum?

A

42

78
Q

Most of the primary x-ray consist of what type of electron interactions?

A

Brammstrahlung

79
Q

If a high speed electron collides with a orbital electron in a k-shell what will be produced?

A

High energy characteristic x-ray

80
Q

When is an atom in an excited state?

A

When one or more electrons are in higher energy levels than usual

81
Q

Where are useful characteristic x-rays produced in tungsten?

A

By ionization of a K-shell electron

82
Q

If too much filtration were to be added what is the effect on the resulting image?

A

Have noise

83
Q

Can increasing x-ray intensity (mAs) ever compensate for inadequate penetration (kVp)?

A

No, increasing mAs will only increase patient dose and will not produce better quality images

Image Prod & Eval (10 decks)

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