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x.umn radiology > Characteristics of X-rays > Flashcards

Characteristics of X-rays Flashcards

1
Q

two mechanisms of x-ray production

A
  • bremsstrahlung

- characteristic radiation

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2
Q

what is bremsstrahlung x-ray production?

A

electron to nucleus interaction

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3
Q

what is characteristic radiation?

A

electron to electron radiation

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4
Q

bremsstrahlung: x-rays produced when ______ are suddenly _____ when they pass close to the nuclei of a ________

A

high velocity e-, decelerated, high Z# absorbing material

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5
Q

3 requirements of Bremsstrahlung radiation

A

electrons, high velocity to electrons, high Z# absorbing material

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6
Q

bremsstrahlung has _____ and ___ interactions

A

direct hit, near-miss

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7
Q

because not all e- attain the same ___, some move at different ___ than others, ultimately producing _________, or__________

A

velocity, velocities, radiation of different energies, polychromatic x-ray beam

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8
Q

what percentage of diagnostic beam is bremsstrahlung?

A

70%

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9
Q

in near-miss bremsstrahlung interactions: the closer the e-, the ________ of the bremsstrahlung photon

A

closer the electron

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10
Q

characteristic radiation: a number of e- with inner orbital electrons of W, overcome the ______, and cause _____

A

binding energies, ionization

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11
Q

result of characteristic radiation is a polychromatic x-ray beam but __________ than bremsstrahlung

A

much narrower energy spectrum

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12
Q

the energy of characteristic radiation is specific to ________

A

the Z of the producing material

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13
Q

what percentage of diagnostic x-ray beam is characteristic?

A

30%

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14
Q

incident electron knocks ______ (____); incident electron may continue as a ______

A

inner electron out (recoil electron), photoelectron

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15
Q

are x-rays electrons?

A

no

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16
Q

electrons are….

A
  • particulate radiation
  • have mass
  • and have variable velocity
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17
Q

x-rays are…

A

-electromagnetic radiation (no mass, fixed velocity)

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18
Q

radiation that originates at focal spot, leaves the tube through window, is useful in image formation

A

primary (usable) beam

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19
Q

radiation that originates at focal spot, leaves the tube through barriers around the tube

A

leakage radiation

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20
Q

radiation that originates in tissues, causes image noise

A

secondary/scatter radiation

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21
Q

what is used to minimize leakage radiation?

A

glass, oil, and metal enclosures

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22
Q

change in kVp changes ________

A

potential difference between cathode and anode

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23
Q

increase kVp does what to the number of photons generated (quantity)?

A

increases quantity

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24
Q

increase kVp does what to the mean energy of the photons (beam quality)?

A

increases quality

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25
Q

increase kVp does what to maximal energy of photons (beam quality)?

A

increases quality

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26
Q

increase kVp does what to radiographic contrast?

A

decreases contrast

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27
Q

For constant receptor exposure, exposure time and kVp are ________

A

inversely related

28
Q

when kVp is increased, ____ should be decreased

A

exposure time

29
Q

most times, we “set and forget” _____ while we change ____

A

kVp and mA; exposure time

30
Q

increase mA, what happens to amount of power applied to filament?

A

increased

31
Q

increase mA, what happens to x-ray beam quality?

A

increasing mA does nothing to beam quality

32
Q

what happens to receptor exposure when we increase mA?

A

increase exposure

33
Q

exposure time does not influence ______

A

energy of the photons

34
Q

mAs is a product of ______(__) and _______(_)

A

tube current (mA), exposure time (s)

35
Q

what is the control of size/shape of x-ray beam?

A

collimation

36
Q

increased collimation leads to…

A

smaller beam, decreased receptor exposure

37
Q
  • circular, diameter at end of cone = ____

- rectangular end of cone = ____

A 
circular = 2.76"
rectangular = 2.0"
38
Q

a rectangular collimation reduced ______

A

patient exposure/dose substantially

39
Q

purpose of filtration

A

preferentially remove long wavelength photons

40
Q

lower kVp results in _______, but the longest wavelength are not useful in _______; they increase patient dose/radiation hazards and _____

A

higher radiographic contrast, image formation; must be removed

41
Q

_____ + ______ = total filtration

A

inherent + added

42
Q

examples of inherent filtration

A

widow of x-ray tube, insulating/cooling oil, oil seal

43
Q

examples of added filtration

A

aluminum discs (1/2mm or 1mm)

44
Q

beam produced at or below 70kVp = ___mm Al equivalent

A

1.5mm

45
Q

beam produced at 90 kVp = ___mm Al equivalent

A

2.5mm

46
Q

if filtration increase, mAs should be ____ to ________

A

increased, maintain similar receptor exposure

47
Q

the thickness of a material which, when placed in the path of an x-ray beam, will reduce quantity of radiation by 50%

A

half value layer (HVL)

48
Q

HVL is an indicator of x-ray beam _____

A

quality (penetrability)

49
Q

a beam with higher mean energy (higher penetrability) has a _____

A

thicker HVL

50
Q

you need to increase HVL with…

A

increased kVp, increased filtration

51
Q

for constant receptor exposure, exposure time should be ____ when SID (source to object distance) increases

A

increased

52
Q

based on inverse square law, exposure time is ______ to the square of SID

A

directly proportional

53
Q

with inverse square law, if you double the distance, intensity becomes ____ the original

A

1/4

54
Q

with inverse square law, if you half the distance, intensity becomes ____ the original

A

4x

55
Q

attenuation in which photon ionizes absorber (tissue) atoms, convert their energy to ejected e-, and then cease to exist

A

absorption attenuation

56
Q

attenuation in which photons interact with
absorber (tissue) atoms, but is deflected in
another direction

A

scattering attenuation

57
Q

3 types of beam attenuation

A
  • coherent scattering
  • photoelectronic absorption
  • Compton scattering
58
Q

how many photons undergo coherent scatterin?

A

7%

59
Q

how many photons undergo photoelectronic absoprtion?

A

27%

60
Q

how many photons undergo Compton scattering?

A

57%

61
Q

did you look at the 3 types of beam attenuation photos on the powerpoint?

A

I hope you did, they sure help!

62
Q

coherent scattering process

A
  1. low energy incident photon interacts with whole photon
  2. atom momentarily excited; photon momentarily disappears
  3. excited atom returns to ground state; release photon
  4. photon absorbed by tissue
63
Q

coherent scattering has a (contribution/no contribution) to image noise

A

no contribution

64
Q

______ and _____ cause secondary and tertiary ionizations

A

photoelectric absorption and Compton’s scattering

65
Q

photoelectric radiation process

A
  1. Incident x‐ray photon interacts with an inner
    orbital electron
  2. Inner electron is ejected; called photoelectron
    or recoil electron (atom is ionized)
  3. higher orbital e- falls to fill vacancy
  4. this “fall” emits electromagnetic energy
66
Q

Compton’s scattering process

A
  1. Incident photon interacts with an outer orbital e-
  2. Overcomes binding energy, ejects e- (ionization)
  3. Ejected e- (called Compton’s electron)
    acquires part of the energy
  4. Remainder of energy given off as scattered,
    weaker energy photon

x.umn radiology (15 decks)

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