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Radiology > LEC 1 - Radiology Principles > Flashcards

LEC 1 - Radiology Principles Flashcards

1
Q

What are the five main parameters for xray?

A 
Grid 
Focus 
mAs 
Field size 
kVp
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2
Q

What are the two things that happen to an xray when it interacts with matter?

A

Absorption
– or –
Scatter

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3
Q

How are x-rays produced?

A

Conversion of kinetic energy of accelerated electrons into alectromagnetic radiation

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4
Q

What 3 major things happen with electrons in the x-ray tube?

A

Production + Acceleration + Deceleration

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5
Q

What is the source of the electrons?

A

Cathode

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6
Q

Where does deceleration occur?

A

Anode

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7
Q

What two forms of energy are the electrons converted into?

A

X-rays
– and –
Heat

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8
Q

What form of energy is created most in the process of producing xrays?

A

Heat

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9
Q

What is the cathode made from?

A

Tungsten

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10
Q

How are electrons focused in an x-ray?

A

Negatively charged metal housing

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11
Q

Term: mA

A

X-Ray tube current

Number of electrons flowing per second from filament to target

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12
Q

What is the problem with increasing mAs?

A

Increased time of exposure
= increased motion in image
= decreased quality

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13
Q

What technically is occurring when you increase mAs?

A

Number of electrons accelerated increases

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14
Q

What is potential difference?

A

kVp

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15
Q

What does a high potential difference lead to?

A

Accleration of electrons in vacuum towards anode

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16
Q

What happens when high speed electrons strike anode?

A

Radiation emitted

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17
Q

What are the two methods that radiation are emitted from an anode?

A

Characteristic radiation
– and –
Bremsstrahlung

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18
Q

What part of energy do you want to filter out of your xray?

A

low energy

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19
Q

What is occurring with Bremsstrahlung?

A

Incident electrons are deflected around nucleus
Loss of energy emitted = xray

– or –
Incident electrons hit nucleus = high energy

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20
Q

What happens if you increase kVp too much?

A

Too much exposure = xray looks black

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21
Q

What is occurring with characteristic radiation?

A

High speed electron hits electron in orbit

= x-ray photon given off

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22
Q

What settings (basic) do you want for lung and abdomen xrays?

A

increased kVp + decreased mAs

- Gray

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23
Q

What settings (basic) do you want for constract/bone xrays?

A

increased mAs + decreased kVp

- Black/white

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24
Q

What exactly happens when you increase kVp?

A

Increase electron velocity
Increase x-ray energy
Increase penetrating power

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25
Q

What are the two stages of an xray?

A

Rotation
– and –
Exposure

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26
Q

What are the characteristics of a small filament?

A

Small electron beam + focal spot

Fine detail, concentrates heat

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27
Q

What are the characteristics of a large filament?

A

Larger electron beam + focal spot

Reduced detail, but higher exposure (mAs)

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28
Q

What does the angle of the anode cause?

A

Heel effect

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29
Q

What is the heel effect?

A

What % of intesity changes as it moves away from the central ray

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30
Q

Where is the % of intensity the highest?

A

Near the cathode

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31
Q

Why is the anode side of the x-ray weak?

A

It has to travel through part of the machine before it reaches the patient

32
Q

Where do you want the cathode anatomically when taking xrays?

A

Proximal

33
Q

Term: Attenuation

A

Decrease in intensity of x-ray beam as it passes through matter

34
Q

Term: Absorption

A

Photon removed from beam

35
Q

Term: Scatter

A

Photon changes direction

36
Q

Term: Transmission

A

X-ray passes through matter without interaction

37
Q

Term: Shadowgram

A

attenuation through different tissues in patient changes intensity producing a picture on the xray

38
Q

Term: Quality of a Beam

A

Penetrating power

Proportional to x-ray enerygy

39
Q

Term: Intensity of a Beam

A

Amount of energy in beam

Proportional to number of photons

40
Q

What are the types of scatter that can occur in an x-ray?

A

Coherent + Photoelectric effect + Compton

41
Q

What is the most important scattering effect that occurs with x-rays?

A

Photoelectric effect

42
Q

What does coherent scattering cause on the film?

A

Film fog

43
Q

What does the photoelectric effect cause on the film?

A

Contrast

44
Q

What does compton scattering cause on the film?

A

Film fog + Increase in hazards

45
Q

What is coherent scattering?

A

Photon interacts with object + changes direction

46
Q

Term: Film fog

A

Decrease in radiographic quality

47
Q

Wha tis the photoelectric effect?

A

Complete absorption of the x-ray photon

Photoelectron removed from shell = IONIZATION

48
Q

What are the factors that determine the probability of PE occurring?

A

Atomic number
– and–
Inversely proportional to x-ray energy cubed

49
Q

What scenario is PE most likely to occur?

A

Low energy photon + High atomic number

50
Q

What does PE do?

A

Magnifies the differences in the tissues

= increased contrast

51
Q

What is the compton effect?

A

Incoming photon ejects free outer shell electron

Photon scatter = lower energy but can produce ionization

52
Q

What are the factors that determine the probability that the Compton effect will occurr?

A

Energy of photon
– and –
Electron density (NOT ATOMIC NUMBER)

53
Q

What is the major result of the Compton effect?

A

Almost all scatter reaches the film

54
Q

What kind of contrast is seen with low kVp

A

High contrast

55
Q

What are the four factors that determine the degree of x-ray absorption?

A

Atomic number of tissue
Density of tissue
Thickness
Photon energy

56
Q

What are the components of radioopacity?

A

Effective Z
– and –
Density

57
Q

What are the five radiopacities? (in order)

A 
(lucent) 
Air 
Fat 
Soft tissue 
bone 
Metal 
(Opaque)
58
Q

Term: Scatter radiation

A

Radiation from sources other than primary x-ray beam

59
Q

What scatter effect produces scatter radiation?

A

Compton

60
Q

What are the three causes of scatter radiation?

A

Thick tissues
Table
Cassette

61
Q

What are the three factors that influence scatter?

A

kVp
Field size
Tissue thickness

62
Q

How is scatter production reduced?

A

Collimation via low kVp + tissue compression

63
Q

How is the effect of scatter on film reduced?

A

Grids + Air gap

64
Q

What are the tissues that tend to be the most responsive to xrays?

A

Bone marrow
Epithelial
GI

65
Q

What effects do xrays have on gonadal cells?

A

Amplified damage due to genetic alterations

66
Q

What effects do xrays have on fetal cells?

A

Death
Congenital malformations
Growth defects

67
Q

What is the stochastic effect?

A

Probabilty of damage occurring increases with dose

68
Q

What effect do xrays have during the first trimester?

A

Fetal death

69
Q

What is the effect of xrays during the second trimester?

A

Developmental anomalies

70
Q

What is the effect of xrays during the third trimester?

A

Delayed growth

71
Q

At what point can you take pregnancy xrays of cats?

A

39 days

72
Q

At what point can you take pregnancy xrays of dogs?

A

42 days

73
Q

What is the inverse square law?

A

Distance from primary source is doubled

Intensity will decrease by a factor of four

74
Q

What is the added filtration in an xray?

A

Aluminium

75
Q

What is the inherent filtration in an xray?

A

Glass envelope
Insulating oil
Plastic tube window

76
Q

Where do monitors for xrays need to be worn?

A

At collar level over apron
– and –
At waist level under apron

Radiology (21 decks)

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