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Radt 1303 Physics > Chapter 7 Exam > Flashcards

Chapter 7 Exam Flashcards

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1
Q

Radiographic density refers to overall _______ on image receptor

A

blackness

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2
Q

Classical interactions has 3 names:

A

classical, coherent scattering, Thompson scattering

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3
Q

What interactions and effects do we deal with the most?

A

classical interactions, Compton scattering, and photoelectric effect

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4
Q

Classical interactions result in:

A

scatter x-rays

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5
Q

high-energy photons interact with random electron and gets deflected in new direction
- Ionizes the atom (makes it unstable)
- Electron leaves the atom with enough energy to have an interaction with another atom close to it
- Results in image fog (also called noise)
- Happens a lot, not good

A

compton scattering interaction

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6
Q

x-ray photons are totally absorbed

A

photoelectric interaction

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7
Q

Increased tissue density _______ radiographic density

A

decreases

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8
Q

Decrease tissue density (ex: adding air) ________ radiographic densities because x-rays can get through easier

A

increases

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9
Q

Increasing tissue density ________ radiopaque

A

increases

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10
Q

Decreasing tissue density ________ radiolucency

A

increases

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11
Q

produces two particles-positron & electron, happens outside of diagnostic imaging

A

Pair production

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12
Q

Incident photon =

A

1.022 MeV (very big)

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13
Q

does not occur in radiography (10 MeV or more)

A

photodisintegration

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14
Q

gives us the ability to have different tissue densities and contrast in an image
The higher the Z number the more dense the atom is and the more likely it is to absorbs

A

differential absorption

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15
Q

____ creates more radiographic density

A

Air

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16
Q

_____ creates less radiographic density

A

Metal

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17
Q

Which of the following is a major source of occupational exposure?

A

Compton interactions

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18
Q

Which interaction, within the diagnostic range, does not involve the removal of an orbital electron?

A

Classical scattering

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19
Q

Which interaction requires 1.02 MeV of energy?

A

Pair production

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20
Q

A photon of 10 MeV colliding with a nucleus will likely result in what type of interaction?

A

Photodisintegration

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21
Q

Which technique will produce the greatest number of photodisintegration events in an average abdomen? 120 kV and 5 mAs, 108 kV and 10 mAs, 98 kV and 20 mAs, none of the above

A

None of the above

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22
Q

Which of the following events will not occur in the diagnostic range of x-ray energies? Classical, compton, photoelectric, photodisintegration

A

Photodisintegration

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23
Q

Positive contrast media is administered to increase what type of interactions?

A

Photoelectric

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24
Q

Which of the following contributes most to image fog? Classical, photoelectric, pair production, compton

A

Compton

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25
Q

Which interaction in the diagnostic range involves the total absorption of the incident photon?

A

Photoelectric effect

26
Q

When the kV selected is equal to or slightly greater than the inner-shell binding energy of a target tissue atom, which interaction predominates?

A

photoelectric

27
Q
  • Also called coherent or
    Thomson scattering
  • The incident x-ray
    photon interacts with
    an orbital electron of a
    tissue atom and
    changes direction
  • Incident wavelength
    equal to scattered
    wavelength
  • Energy below 10keV
    (little importance to
    diagnostic x-ray)
A

classical interactions

28
Q

An incident x-ray photon
enters a tissue atom,
interacts with an orbital
electron, and removes it
from its shell; it loses up to
one third of its energy and
is usually deflected in a new
direction

A

compton interaction

29
Q

compton interaction formula

A

Ei = Es + (Eb + Eke)
Ei = incident photon energy
Es = scatter photon energy
Eb = electron binding energy
Eke = photoelectron kinetic energy

30
Q

ionizes the atom making it unstable
the ejected electron leaves the atom with enough energy to go through interactions of its own adjacent atoms
the incident photon is deflected in a new direction and is now a compton scatter photon with enough energy to go through other interactions in the tissues or exit the patient and interact with the image receptor

A

compton interactions

31
Q

Is one of the most prevalent interactions between x-ray
photons and the human body in general diagnostic
imaging

A

compton scatter

32
Q

Probability NOT dependent on the atomic number of
atoms involved but is related to the energy of the
photon

A

compton scatter

33
Q

The incident x-ray photon interacts with the inner-shell electron of a tissue atom and removes it from orbit

A

photoelectric interactions

34
Q

The tissue atom is ionized and the inner-shell vacancy makes the
atom unstable
To regain stability, a ________________ occurs, producing secondary x-ray photons
These secondary photons are of low energy, are absorbed by the body in other photoelectric events, and contribute to patient dose

A

characteristic cascade
photoelectric interactions

35
Q

photoelectric interaction equation

A

Ei = Eb + Eke
Ei = Incident photon energy
Eb = Electron binding energy
Eke = Photoelectron kinetic
energy

36
Q

The probability of photoelectric interaction
depends on the following:

A

The atomic number of the tissue atoms with which they interact
The incident x-ray photon energy

37
Q

factors affecting the photoelectric-compton ratio

A

Z# of the material
Photon energy

38
Q

Occurs when the incident x-ray photon has enough energy to escape interaction with the orbital electrons and interact with the nucleus of the tissue atom

A

pair production

39
Q

Produces two
particles: a positron
and an electron

A

pair production

40
Q

For these particles to exist, they must each
have energy of 0.51 MeV.
Both particles travel out of the atom.
The electron undergoes many interactions
before coming to rest in another atom.
The positron travels until it strikes an electron,
causing an annihilation event.
Does not occur in
radiography

A

pair production

41
Q

Occurs when photons with extremely high energies strike the nucleus of the atom and make it unstable
The nucleus of the atom involved regains stability by ejecting a nuclear particle
Does not occur in radiography (10 MeV or more)

A

photodisintegration

42
Q

The difference between x-ray photons that are absorbed photo-electrically versus those that penetrate the body
Different body structures absorb x-ray photons to different extents

A

differential absorption

43
Q

those photons
that are attenuated by the
body and do not reach the
image receptor

A

absorption

44
Q

those x-ray photons that pass through the body and reach the image receptor

A

transmission

45
Q

factors affecting differential absorption:

A

higher atomic number (Z), increased kVp, increased mass density

46
Q

what are the three most common effects in radiobiology:

A

main-chain scission
cross-linking
point lesions

47
Q

which of the following is NOT one of the five basic x-ray interactions with matter?

A

bremsstralung

48
Q

after compton scattering, the scattered x-ray has:

A

longer wavelength

49
Q

the probability that an x-ray will interact with an outer-shell electron is influenced principally by:

A

the energy of the incident x-ray

50
Q

the compton effect is:

A

independent of Z

51
Q

which term describes how different body structures absorb x-ray photons to different extents?

A

differential absorption

52
Q

how does a higher atomic number (Z) affect PE absorption?

A

increases PE absorption

53
Q

how does a higher atomic number (Z) affect compton scatter?

A

compton scatter is unaffected

54
Q

how does a higher atomic number (Z) affect transmitted x-rays?

A

decreased transmitted x-rays

55
Q

how does higher kVp affect PE absorption?

A

decreases PE absorption

56
Q

how does higher kVp affect compton scatter?

A

relatively increases compton scatter

56
Q

how does higher mass density affect PE absorption?

A

increases PE absorption

56
Q

how does higher kVp affect transmitted x-rays?

A

increases transmitted x-rays

57
Q

how does higher mass density affect compton scatter?

A

increases compton scatter

58
Q

how does higher mass density affect transmitted x-rays?

A

decreases transmitted x-rays

Radt 1303 Physics (8 decks)

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