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veterinary science 2.1 > radiography (wk 1) > Flashcards

radiography (wk 1) Flashcards

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1
Q

definition of radiographic detail?

A

detail means how much definition you have on the edge of an anatomical structure

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2
Q

what factors affect radiographic detail?

hint - six

A
  • movement (animal or equipment)
  • source to image detector (SID) distance
  • object to film distance (OFD)
  • distortion
  • collimation
  • exposure factors
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3
Q

what does SID stand for?

A

source to image detector (SID) distance, which is the distance from the x-ray tube to the image detector

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4
Q

what does OFD stand for?

A

object to film distance (OFD) - this is the distance between whatever you’re trying to x-ray and the detector plate

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5
Q

You want to take a radiograph of this dog’s left stifle. How should you position the dog on the x-ray table?

A

in left lateral recumbency (left side down) - this means the area of interest will be closest to the image detector

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6
Q

what is collimation?

A

coning of the primary x-ray beam to control it’s size and shape (done with led shutters, I think?)

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7
Q

The area of interest should always be parallel or perpendicular to the x-ray beam - what happens otherwise?

A

distortion (creates a misleading perception of the size of a structure, and may also result in loss of fine detail)

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8
Q

how does collimation improve image detail?

A

it focuses the x-ray beam on the area of interest, giving better visualisation of small structures and details

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9
Q

what is radiographic density?

A

the overall darkness or blackness of the radiographic image

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10
Q

what influences radiographic density?

A

the amount of X ray exposure received by the image detector (as well as the density of the tissue and it’s capacity to absorb x-rays.

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11
Q

how can we increase radiodensity?

A

adjusting exposure factors, either:
- more x-rays (higher mAs) or
- a more penetrating beam of x-rays (higher kV)

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12
Q

what’s radiographic contrast?

A

the visible difference in radiographic density between areas next to each other on an x-ray (how we identify different organs/tissues)

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13
Q

what does high contrast mean?

A

large density difference, appears very black and white. good for fine details/bony structures

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14
Q

what does low contrast mean?

A

small density difference (shades of grey). good for imaging soft tissues/highlighting subtle differences

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15
Q

signs of underexposure (not enough x-ray beams) in radiographs?

A

a mottled or speckled, grainy appearance

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16
Q

signs of overexposure (too much xrays) in radiographs?

A

“tissue burnout”, in other words soft tissue/definition of soft tissue disappearing (missing penis x-ray). image looks washed out

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17
Q

what is an artefact in a radiography context?

A

anything that shows up on an image that is not part of the animal being x-rayed, eg collars, dirt in fur. note - apparently microchips count as part of the animal

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18
Q

what are orthogonal views?

A

multiple x-ray views of a structure taken from different directions or angles (eg at right angles/perpendicular to each other, like lateral and ventrodorsal)

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19
Q

are foam wedges radiolucent or radiopaque?

A

radiolucent, x-ray beams can pass through them

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20
Q

are sand bags radiolucent or radiopaque?

A

radiopaque, x-ray beams cannot pass through them (don’t use in the primary beam, will be a white blob)

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21
Q

what is a legal requirement to identify/label x-rays with?

A

Date
Patient’s name
Owner’s name
Clinic name
Left and Right markers
Any other relevant information (eg microchips)
- DICOM files are accessible worldwide

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22
Q

what is ionising radiation?

A

radiation strong enough to remove electrons from atoms to create ions

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23
Q

examples of ionising radiation?

A

gamma rays and x-rays (significant health risks)

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24
Q

examples of non-ionising radiation?

A

infrared, microwaves, visible light, radiowaves (not a significant health risk)

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25
Q

what’s acute radiation injury?

A

tissues exposed to sudden and very high doses of radiation, eg anatomic bombs. death occurs in a few days.

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26
Q

what’s chronic radiation injury?

A

tissues exposed to frequent, small dose radiation exposure, which cumulatively add up over the years. radiation induced cancers may take 10-20 years to appear.

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27
Q

what’s the difference between somatic and genetic affects on radiation?

A

somatic directly affects the body exposed to radiation, genetic damages cells of the reproductive system meaning the person is fine, but their kids are affected.

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28
Q

factors that affect radiation dose impacts on health?

A

sensitivity of the tissue to x-rays, radiation dose, type of radiation, duration of exposure

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29
Q

examples of tissues especially sensitive to radiation?

A

bone marrow, thyroid glands, reproductive organs, intestines.

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30
Q

what is the relevant legislation to be followed in New Zealand regarding radiation?

A
  • radiation safety act 2016
  • radiation safety regulations 2016
  • code of practise for veterinary radiation
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31
Q

what are the components of a radiation safety plan? (hint, there’s four)

A
  • radiation safety policies
  • standard procedures
  • record keeping
  • staff training
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32
Q

what does ALARA stand for?

A

as low as reasonably achievable (the radiation safety principle)

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33
Q

what are the three safety principles that help us to achieve the ALARA principle?

A
  • time
  • distance
  • shielding
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34
Q

what can we do to reduce the amount of time we are exposed to x-rays

A
  • sedation and positioning aids (reduce need to hold animals)
  • take care with positioning to minimise need to retakes
  • remove people not needed from room
  • rotate staff
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35
Q

what is the inverse square law for radiation?

A

if you double your distance away from the source, you quarter your dose (reduce by 75%)

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36
Q

ways we can use distance to reduce x-ray dose exposure?

A
  • stand far way
  • avoid using portable units by hand
  • use cassette holders when x-raying large animals
  • collimate the primary beam
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37
Q

what is lead shielding available in?

A
  • gowns
  • thyroid collars
  • gloves
  • glasses
    note: they do not block the primary beam, just scatter radiation
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38
Q

true or false - stochastic effects are directly related to the radiation dose administered

A

false - these are effects that occur by chance, generally occurring without a threshold level of dose, the main ones being cancer and genetic effects.

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39
Q

x-rays are a type of electromagnetic radiation, but are characterised by what?

A

a short wavelength and high frequency

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40
Q

do x-rays have a higher or lower frequency than visible light?

A

higher

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41
Q

components of an x-ray tube?

A

high voltage supply (from outside)
lead shielding walls of tube
vacuum chamber
cathode filament
anode/target
filter

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42
Q

purpose of the cathode filament (filament of metal with high boiling point that gets heated)

A

it produces electrons (they’re “boiled” off when filament is heated)

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43
Q

is the cathode positively or negatively charged

A

negatively (opposite to cations and anions)

44
Q

what is the process of thermionic emission?

A

production of electrons though heating the cathode filament so electrons “boil” off

45
Q

what is the purpose of the high voltage field?

A

it sits between cathode and anode to accelerate electrons

46
Q

what is the purpose of the vacuum chamber in the x-ray tube?

A

it removes obstructions to the electrons, eg air molecules, that block their path. means electrons reach anode with high KE

47
Q

what is the purpose of the anode/target?

A

to convert electron KE to x-ray photons when they collide with the anode (electron KE –> X-ray photon + heat (99%))

48
Q

why does the anode rotate?

A

to distribute heat (99% of the electron KE –> x-ray photon reaction is lost as heat).

49
Q

purpose of lead shielding of x-ray tube?

A

to contain stray electrons and x-rays, absorbs radiation. there is a gap/window in the shielding towards patient.

50
Q

purpose of the filter in the x-ray tube/over gap in lead shielding?

A

to absorb low energy photons (get absorbed by soft tissue and add to radiation dose but have no useful contribution), lets high energy photons pass through. often a thin sheet of aluminium.

51
Q

is the anode positive or negative?

A

positive (opposite to cations and anions)

52
Q

what are the two most important factors of the electrical supply?

A

the transformer and rectifier

53
Q

what does a rectifier do (electrical supply)?

A

to transfer electrical energy from an alternating current (AC) into direct current (DC) across the x-ray tube, so that the electrons flow in one direction from the cathode to anode

54
Q

what does a transformer do (electrical supply)

A

increase the voltage from the power source to a high enough level for x-ray production

55
Q

what is the purpose of the control panel on an x-ray machine?

A

turn on/off machine, and to adjust the exposure factors, X-ray tube voltage (kVp), and x-ray tube current and exposure time (mAs).

56
Q

what is the primary beam?

A

x-ray photons when they emerge from the x-ray tube

57
Q

what is a photon?

A

a tiny particle/electric field, made up of waves of electromagnetic radiation

58
Q

what is an LBD, and it’s purpose?

A

the light beam diaphragm (LBD) allows us to “see” the area the X-rays will land.

59
Q

what are the the two stages of the exposure button used to take an x-ray?

A

1 - prep - the top button is pushed town to heat the filament and start the anode rotating
2 - expose. pressing both buttons down sets up the electrical field between cathode and anode, x-rays are produced.

60
Q

what is the purpose of the image detector?

A

it’s the device used to capture the x-ray images into a digital format (usually either built into the table, or in some sort of portable format)

61
Q

benefits of stationary x-ray tubes?

A

compact size, less expensive, lighter and more portable, simple and robust design.

62
Q

benefits of rotating anodes?

A

more effective heat dispersion, can generate higher energy x-rays

63
Q

what’s another name for the collimater?

A

a light beam diagram (LBD)

64
Q

what’s the purpose of the collimator/LBD?

A

to control and restrict the size and shape of the x-ray beam (process called collimation or coning), as well as a light source used as a guide for where the x-ray beam will go

65
Q

what’s the abbreviation for x-ray voltage?

A

kVp

66
Q

what does kVp mean?

A

x-ray voltage (kilovoltage peak), it’s the peak voltage applied across the x-ray tube (cathode to anode acceleration)

67
Q

what does kVp (x-ray voltage) control?

A

how much energy/how penetrating the x-ray beam is (how hard you throw the handful of pebbles) - refers to the quality of the x-rays in primary beam

68
Q

would you need higher kVp settings for a duckling or a labrador?

A

labrador - the higher the kVp, the more penetration

69
Q

what does mAs stand for?

A

millimperes per second (amount of current applied to cathode filament)

70
Q

what does mAs/millamperes per second do?

A

impacts the amount of electrons “boiled” off the cathode filament –> travelling to anode –> x-ray photons produced. intensity and brightness. (the number of pebbles in the handful you’re throwing at the wall) refers to the quantity of x-rays in primary beam

71
Q

what does mAs combine?

A

mA (milliamps) and time (seconds). the more current applied to the filament the more electrons are boiled off, and the longer it’s heated the more electrons you get - can use different combinations of mA and time to get the same mAs

72
Q

why are shorter exposure times normally used in veterinary practise?

A
  • animals don’t keep still or hold their breath very well
  • better resolution, sharper image
  • lower radiation doses
73
Q

why are x-rays not absorbed evenly by the body?

A

different tissues have different densities, eg lung tissue isn’t very dense, low absorption, vs bone, complete absorption

74
Q

what does radiographic opacity (or radiopacity) mean?

A

“the property of a material or structure to block or absorb x-rays”. shows up whiter or brighter, eg metals

75
Q

what does radiographic lucency (or radiolucency) mean?

A

“the property of a material or structure to allow x-rays to pass through”, appears blacker or darker eg air.

76
Q

the five degrees of radiopacity from least to most radiopaque?

A
  • air
  • fat
  • water
  • soft tissue and fluid
  • mineral/bone
  • metal
77
Q

why does scatter radiation occur when taking x-rays?

A

Instead of passing directly through the body to create an x-ray image, some x-rays interact with atoms in the animal’s body or other objects, resulting in a change of direction.

78
Q

how can you minimise amount of scatter radiation produced?

A
  • collimating primary beam as much as possible (scatter increases with larger area)
79
Q

why is scatter radiation problematic?

A

it contributes to the overall radiation dose, and degrades image quality (does not increase exposure time though)

80
Q

how are dorsal/ventral radiographic projections named?

A

by the point of entry followed by point of exit of the x-ray beam, eg dorsoventral - beam enters at the dorsal aspect, exits through the ventral aspect.

81
Q

a dog is lying on it’s stomach, back facing upwards - what radiographic projection is being produced?

A

dorsoventral (DV)

82
Q

a dog is lying on it’s back, stomach facing upwards. what radiographic projection is being produced?

A

ventrodorsal (VD)

83
Q

how are lateral radiographic projections named?

A

by the side that is closest to the image detector in the table - eg a dog lying in lateral recumbency with it’s left side facing up would produce a right lateral projection

84
Q

how are x-rays using caudal and cranial named?

A

same as dorsal/ventral - entry point of x-ray first, followed by exit, but with side of animal included in front eg left craniocaudal

85
Q

what is “conventional” (traditional) radiography storage?

A

film based, x-rays are captured using film cassettes positioned under or behind the animal. after exposure and chemical baths, image is viewed on a lightbox. (this method has largely been replaced by digital systems)

86
Q

what are the two types of digital radiography?

A

Direct digital radiography (DDR) - X-ray detectors directly capture the radiation and convert it into a digital image.
and
Computed radiography (CR) - The image is obtained using a phosphor plate that captures x-ray radiation. After exposure, the plate is scanned by a laser, and the information is converted into a digital image.

87
Q

how are digital x-ray images stored?

A

as DICOM (Digital Imaging and Communication in Medicine) files - this is the international standard.

88
Q

Viewing ventrodorsal and dorsoventral projections - how should the animal in image be positioned?

A

head at the top of the image, animal’s right side on viewer’s left (like the animal is standing on it’s hind limbs, facing us)

89
Q

Viewing lateral projections - how should the animal in the image be positioned?

A

with the head to the left and the spine at the top of the image

90
Q

how is an x-ray different to a radio wave in terms of wavelength?

A

it has a much shorter wavelength (and higher frequency)

91
Q

what captures the x-ray image in a digital format?

A

the detector (image detector)

92
Q

what controls exposure factors?

A

the control panel

93
Q

what enables accurate positioning of the x-ray beam?

A

light beam diaphragm/collimator

94
Q

what produces x-rays?

A

the x-ray tube

95
Q

what supplies voltage and direct current?

A

the electrical supply and rectifier

96
Q

what heats the filament and sets up an electrical potential across the x-ray tube?

A

the exposure button

97
Q

what contains x-rays of differing energies?

A

the x-ray beam

98
Q

if your area of interest for a radiograph is a long bone, the view should include…?

A

the joints above and below

99
Q

If your area of interest is a joint, the view should include…?

A

1/3-1/2 of the bones proximal and distal to the joint of interest.
(The exception to this is for the phalanges, where the entire phalange is included if the metacarpal/metatarsal phalangeal joint is included)

100
Q

The closer the object of interest is to the detector, the more accurately the image is captured. As the object-detector distance increases, the image will appear larger and less clear, as a result of……?

A

magnification

101
Q

In the body, many structures are in the same plane. When this information is converted to a 2 dimensional image, these structures overlap, a term known as…..?

A

superimposition

102
Q

When 2 objects of the same radiodensity are in contact with each other, the margins of the objects will be impossible to distinguish from each other, this is known as…..?

A

border effacement - In order to distinguish objects on radiograph, you need tissues of different density

103
Q

within 2m of the irradiating apparatus, you must wear PPE. this includes…?

A

lead gloves, lead thyroid protection, lead gown and in certain situations lead glasses (which are somehow transparent)

104
Q

Are all tissues of the human body equally sensitive to radiation?

A

no - the more cell division occurs, the more sensitive they are (lens of eyes and thyroid glands esp. sensitive)

105
Q

Is protective clothing used during radiography protective against both the primary x-ray beam and scatter radiation?

A

nope - only scatter radiation

106
Q

Doubling the distance from the x-ray machine, reduces your radiation exposure by 50% or 75%?

A

75% - tripling reduces it by 89%

107
Q

what does orthogonal mean?

A

at right angles

veterinary science 2.1 (22 decks)

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