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arrt prep > Radiation safety: principles of radiation protection > Flashcards

Radiation safety: principles of radiation protection Flashcards

1
Q

x-ray production requires 4 conditions. What are they?

A

1.) source of free electrons
2.) acceleration of electrons
3.) focusing of electrons
4.) deceleration of electrons

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2
Q

Source of free electrons

A

The source of electrons is a filament at the cathode end of the tube.
The current is passed through the tungsten filament and heats it up.
-as it’s heated up the increased energy enables electrons to be released from the filament through thermionic emission.

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3
Q

what does the filament consist of?

A

Small coil of tungsten wire

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4
Q

As tungsten is heated…..

A

electrons in the tungsten atoms orbits spin faster, moving farther from the nucleus.
-electrons in outer orbits are flung out of the atoms forming an “electron cloud” or space charge

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5
Q

The space charge provides…..

A

the electron source for x-ray production

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6
Q

If you increase the mA, you increase the _______ current, which in turn increases the _______ current- this leads to more x-ray photons being created.

A

filament; tube

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7
Q

Acceleration of electrons

A

The free electrons must be accelerated across the x-ray tube from cathode to anode

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8
Q

Kvp forces electrons across the tube giving them what kind of energy

A

kinetic energy

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9
Q

The higher the kvp the more energy the ________ electrons will have

A

accelerating
“Pre-workout”

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10
Q

Focusing of electrons

A

a focusing cup houses the filament wires
-made of molybdenum or nickle

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11
Q

if you increase kvp then what else increases?

A

-electron energy increases
-x rays energy increase

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12
Q

when the kvp is applied during the exposure the electrons are focused…

A

-into a narrow beam
-directed from the cathode to the anode

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13
Q

deceleration of electrons

A

the electrons decelerate when they strike the anode

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14
Q

what is the anode target made out of?

A

Tungsten disk which has a high atomic number of (74) and a high melting point
-rehenium makes it last longer **

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15
Q

what are the 2 possible Target interactions?

A

There are two interactions that occur at the target (anode)
-Brems
-Characteristic
** BOTH start with an electron and result in a photon

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16
Q

X-Ray Productions happens…..

A

In the tube!! at the anode target

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17
Q

Explain Bremsstrahlung

A

-Braking radiation
-Electron in & a photon out
-Produces x-rays of all energies
-90% of all x -ray production
-x-rays below 70 KVP are a 100% Brems!

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18
Q

Explain Characteristic

A

-Electron in & Photon out
-The incident electron Collides with a shell electron, crashing it out of orbit and causing a cascade of electrons to fall into each shell closer to the nucleus, each time an electron cascades it causes characteristic x-rays closer to the nucleus to have a higher photon energy

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19
Q

What is K-shell binding energy of Tungsten?

A

69.5 or 70 keV

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20
Q

what is the Frequency of an X-ray mean?

A

It’s the number of times per second the electric and magnetic fields generate themselves.
** Number of waves

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21
Q

The higher the energy of the x-ray, the _______ the frequency

A

higher

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22
Q

what is the Unit of frequency?

A

Hertz (Hx)
or cycles per second

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23
Q

What is wavelength mean?

A

It is the distance the X-ray travels during one regeneration of electric and magnetic fields.
* the distance between two successive peaks. ALSO MEANS: Distance between the tops of the waves.

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24
Q

What is the unit of Wavelength?

A

Angstrom

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25
Q

Frequency and wavelength have an ________ relationship

A

inverse
if frequency increase than wavelength decreases

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26
Q

higher frequency would have either short or a long wavelength. which one?

A

SHORT

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27
Q

Low frequency will either have a short or long wavelength. which one?

A

LONG wavelength

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28
Q

Energy (kvp) and Frequency have a ________ relationship

A

direct
** E&F= closer together in the alphabet

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29
Q

Energy (Kvp) and wavelength are _______ related?

A

inversely
*meaning if you increase kvp, you will get shorter wavelengths!

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30
Q

low frequency

A

extremities!

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31
Q

high frequency

A

chest x ray
where we use a high kvp

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32
Q

beam characteristics

A

-quantity (# of x ray photons)
-quality (energy or the x-ray photons)

33
Q

Quality

A

-the energy of the x-ray photons
-the ability to penetrate
-the KVp determines the quality (energy) of the x-ray beam
-the higher the kvp, the higher the quality of the beam

34
Q

Quantity

A

Refers to the number of x-ray photons
-mAs determines the quantity (number)
-higher the mA= the higher the quantity
-think money-more money = more quantity

35
Q

Primary beam

A

refers to the x/rays that are produced by the x-ray tube and strike the patient
-either brems, characteristic or BOTH

36
Q

Remnant beam or exit beam

A

means remaining
-the remaining beam after it leaves (exits) the patient
-made up of primary and secondary radiation

37
Q

describe the inverse square law

A

the inverse square law states that the intensity of radiation is inversely proportional to the square of the distance between the x-ray tube and the image receptor

38
Q

inverse square law formula

A

I1/ I2 = (D2)^2/ (D1)^2

39
Q

when distance is doubled…..

A

intensity is decreased by 4 times

40
Q

When distance is cut in half…..

A

intensity is increased by 4x
* go basic, as radiographers we know that standing farther from the source reduces dose!

41
Q

10 fundamental properties of x-rays

A
  1. Travel in straight lines
  2. Highly penetrating, invisible rays
  3. electrically neutral
  4. wide range or wavelengths (heterogeneous)
  5. travel at the speed of light
  6. capable of ionizing matter
  7. cannot be focused by a lens
  8. effects digital images
  9. causes certain crystals to fkuroesce
  10. produces secondary and scatter radiation
42
Q

what are the 3 interactions with Matter that occur in diagnostic radiology

A
  1. Compton effect- x ray changes direction
  2. Photoelectric absorption- complete absorption
  3. Coherent- (classical scatter) least likely to happen
43
Q

Explain Compton effect

A

-Most common interaction/ least desirable
-energy partially absorbed by loosely bound outer shell electrons
-knocks electron out of orbit= ionization
-produces scatter photon ( low energy ) going in different direction & Compton electron
-source of the most occupational exposure… REMEMBER Compton = teCh exposure
-straight OUT of compton
-source of the MOST FOG seen on IR
-decreases image contrast

44
Q

Photoelectric effect

A

-photon in
-photon energy equals binding energy
-Total absorption* interaction
-inner shell electron* knocked out of orbit= Ionization
-The ejected electron is termed a “ photo electron”
-Photoelectric = Patient

45
Q

what does attenuation mean?

A

the reduction in intensity of the x-ray beam as result of absorption, scatter and divergence

46
Q

what is differential absorption?

A

different objects absorb radiation differently

47
Q

Thickness of the body part

A

More dense areas of the body will attenuate more x-rays
(abdomen vs. chest)

48
Q

type of tissue

A

the higher the atomic number of the body part the greater the attenuation of the x-ray beam and the greater the biological effect

49
Q

subject density

A

Air - does attuenate
Fat
Water
Muscle
Bone - attuenuates a lot
indirect relationship with receptor exposure
metal

50
Q

Higher frequency to lower frequency

A

-gamma rays
-x-rays
-ulta violet
-visible light
-infrared
-microwave
-radio

51
Q

what to know that brems is

A
  • electron in
    -a target reaction
    -bends or breaks
    -goes around the nuclues
    -if the kvp is lower than 70 its brems
52
Q

what to know about chacteristic

A

-electron in
-cascade effect or cascading!!
-the binding energy of k shell is 69.5 Kev or sometimes they write 70
-“if there a kardesion they would start with the K shell”

53
Q

important fundmental properties of x-ray (not all but important ones)

A

1.Travel in straight lines
2.Electrically neutral, no mass
3.Wide range of wavelengths (heterogeneous)
4. Travel at the speed of light
5. Capable of ionizing matter

54
Q

scatter radiation is what?

A

Scatter radiation is a type of secondary radiation that
occurs when the beam intercepts an object, causing
the X-rays to be scattered.

55
Q

The higher the kvp, the _______ the energy, the _______ the frequency and the __________ the wavelength

A

-higer
-higher
-shorter

56
Q

Kilovolts controls how _______ the electrons are sent
across the tube (tube potential)

A

fast

57
Q

kvp controls

A

Beam Quality
○ Subject Contrast (not digital image contrast)
○ Beam Energy
○ Penetrability

58
Q

Increasing kVp also _________ scattered photons
reducing image quality

A

increases
-Most kVp settings are set per thickness of bone on
technique charts

59
Q

Milliamperage (mA) is a measurement of x-ray tube _________.

A

current

60
Q

Increase mA =

A

increase the filament temperature which increases the electrons boiled off from thermionic
emission.

61
Q

mA determines the _________ of x-ray photons.

A

number

62
Q

exposure time

A

Time or length of exposure is in seconds or fractions of a second.
● 1 second
● 1000 milliseconds
○ Move the decimal point 3 places for milliseconds conversion
Should be kept as short as possible, for most examinations.
● Minimize the risk of patient motion
○ Motion on a radiograph = blurry areas - poor detail
● Longer exposure times increase patient dose.

63
Q

mAs is the main controller of

A

receptor exposure

64
Q

If the patient has more tissue (mass) surrounding the part
than the average patient, you will need to __________mAs.

A

increase

65
Q

quantum mottle

A

not enough mAs
Underexposed image.
● Grainy appearance
● General rule = double original mAs
○ Must increase at least 30% for a visual change
● Follow Exposure Index guides for ranges

66
Q

mAs does not effect

A

-scatter
-contrast
-spatial resolution
-distortion

67
Q

mAs Reciprocity Law

A

There are multiple ways to combine mA and seconds to equal the same mAs.
The reciprocity law shows us that mA and Time are inversely proportional.
They go in opposite directions!
● If mA is Increased - seconds will need to be decreased
● If seconds are increased - mA will need to be decreased
General Rules
1. If mAs is doubled - Time should be cut in half
2. If mAs is cut in half - Time will need to be doubled.
May be used to prevent motion unsharpness.

68
Q

higher receptor exposure?

A

pick the highest mAs

69
Q

reduce motion or prevent it?

A

pick the shortest seconds

70
Q

pediatrics

A

short time!!!

71
Q

coherent scatter

A

-photon in, photon out
-occurs at low energy
-NO effect on patient or occupational
-occurs at low energy

72
Q

a hyperstenthic patient would absorb ________ x- ray photons

A

more

73
Q

ashenic/ hyposthenic will allow __________ more x -ray photons to pass through

A

more

74
Q

increasing kvp will _________ attenuation

A

decrease

75
Q

increasing kvp will __________ absorption

A

decrease

76
Q

increasing kvp will ____________ subject contrast

A

decrease

77
Q

increasing kvp __________ the energy

A

increases

78
Q

increasing kvp _________ the frequency

A

increases
(higher frequency)

79
Q

increasing kvp __________ the wavelength

A

decreases
(shorter wavelength)

arrt prep (24 decks)

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