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vtt 112 - diagnostic imaging > wk 1-3 > Flashcards

wk 1-3 Flashcards

1
Q

what is the difference in visual densities between organs

A

contrast

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2
Q

changes in mAs can directly control the ___ on an x-ray

A

density

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3
Q

if a radiograph has been exposed but not developed or fixed it will be what color

A

purple

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4
Q

how is grid cut off created

A

when the lead strips, bucky, and tube aren’t lined up

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5
Q

is it true that cassettes placed in a bucky tray require more mAs than a table top exposure

A

true

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6
Q

to determine KVp for an exposure, you must ____

A

measure thickness of tissue

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7
Q

the KVp controls the x-ray beams ___

A

voltage power

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8
Q

the length of time a film is left in the developer depends on what

A

temperature of developer solution

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9
Q

if a film has been exposed correctly but after going through the darkroom comes out with an image that has purple tinge all over it, what was the problem

A

the fixer solution washed unsensitized crystals

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10
Q

a film which has been developed and fixed correctly but comes out black was probably a problem with what?

A

too much exposure to white light, pressure, heat, or radiation - all crystals were sensitized and purple was washed off

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11
Q

the scale of contrast that is desirable on a radiograph of the pelvis Is what?

A

short scale contrast

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12
Q

a grid is used to do what?

A

prevent scatter radiation by attracting weak electrons; can affect our safety and cause film fog

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13
Q

intensifying screens allow more or less radiation to be used to expose the film than the same view taken without screen?

A

less; acts as catalyst and intensifies radiation

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14
Q

radiographs for abdominal tissue require the use of what

A

base mAs

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15
Q

how many inches is the commonly used animal focal film distance

A

40 inches

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16
Q

why would the film have come out of the darkroom clear

A

developer didn’t see any sensitized crystals so fixer washed it all away; or put straight into fixer solution

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17
Q

film is left in the fixer solution for

A

twice the time it was in the developer solution

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18
Q

the purpose of the collimator

A

reduce exposure area and scatter radiation

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19
Q

the down leg of the animal will appear smaller or larger than the top leg?

A

smaller

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20
Q

two things that can cause distortion

A

magnification
patient movement
tube movement

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21
Q

diagnostic radiology

A

medical specialization that involves undertaking a range of imaging procedures to obtain images of the inside of the body

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22
Q

ionizing radiation

A

when radiation carries enough energy to ionize atoms or molecules (ionization is the addition or removal of an electron from an electrically neutral atom)

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23
Q

primary radiation

A

unaltered radiation existing at the same energy level as when it was created (hand on table in grid)

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24
Q

secondary radiation

A

scatter radiation; an intersection between primary radiation and matter (bouncing off onto person)

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25
Q

inside the x-ray tube

A

cathode
anode
heel effect

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26
Q

cathode

A

negatively charged side of X-ray tube containing filament (coil of tungsten wire) and focusing cup (repels electron cloud towards anode)

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27
Q

anode

A

positive charged side of X-ray tube containing focal spot (electron beam aimed at spot on target), rotating anode (if it resolves it can withstand more heat and heavier usage), and stationary anode (remains fixed in one place)

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28
Q

heel effect

A

beam varies in intensity as it comes out of the tube - the thicker end of the animal should be placed at the cathode end

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29
Q

low voltage side/filament circuit

A

responsible for supplying voltage to the filament in the xray tube so electrons can be boiled off

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30
Q

stepdown transformer

A

(low voltage) decreases amount of incoming line voltage to the filament in the cathode - heat filament and create electron cloud

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31
Q

MA selector

A

(low voltage) milampule (density); controls number of electrons produced by filament - regulates the current (more amperage into filament, hotter the tungsten wire gets

32
Q

xray tube

A

(low voltage)

33
Q

high voltage circuit

A

produces high voltage across the xray tube so the electron cloud created by the cathode moves across the tube

34
Q

autotransformer (KVP) selector

A

(high voltage) contrast; provides a variable but predetermined amount of voltage to the step up transformer (determined by thickness, controls contrast of image)

35
Q

step up transformer

A

(high voltage) increases voltage to a point high enough to produce xrays

36
Q

rectification

A

process of changing alternating current to direct current by blocking or reversing the negative portion of the wave

37
Q

self rectification

A

xray tube acts as rectifying unit

38
Q

half wave rectified

A

negative portion of current cycle is blocked by installed electrical mechanical apparatus

39
Q

full wave rectified

A

xray machine can reverse the negative cycle to utilize the entire wave with additional valve tubes

40
Q

three phase generators

A

impose three signal phase currents together so there are no deep valleys between electrical pulses

41
Q

film composition

A
  • consists of a layer of silver halide emulsion on both sides of polyester sheet
  • when exposed to light the crystals are sensitized by heat, light, pressure
42
Q

latency

A

always present, needs catalyst to be expressed and visible

43
Q

speeds of film

A

high (fast), slow (more detail); film with larger crystals in thicker layer will react quicker

44
Q

latitude

A

films ability to produce shades of gray

45
Q

cassettes

A

holds xray film and intensifying screens

46
Q

intensifying screens

A

increase the efficiency of the xray beam by glowing when struck by radiation; high (regular with thicker crystals), par (medium), detail (slow with smaller crystals)

47
Q

composition of intensifying screens

A

crystals will glow when struck by light

48
Q

technique of intensifying screens

A

mAs is increased 2 times between high to par; 4 times form par to detail

49
Q

development process (dark room)

A

developer solution
water bath
fixer solution
final wash
automatic processor

50
Q

developer solution

A

sensitizes the crystals to create black

51
Q

fixer solution

A

removes unsensitized crystals and hardens the film

52
Q

automatic processor

A

has a set of rollers to push the film through the stages

53
Q

CR

A
  • uses erasable film in cassette
  • cassette is processed
  • CR traps image by photostimulable phosphor
  • then image appears
    *eliminates wet processor and chemicals
    *short wait for image display
    *reasonable cost for cassettes
    BUT
    *cassettes need to be serviced and prone to scatter radiaiton
54
Q

DR

A

more popular (like camera)
- uses plates
- transfers radiation to digital receptors
- digital data is collected and sent to computer
*fast, good quality, able to manipulate, sends electronically
BUT
*expensive, plates are easily damaged, and software updates are needed

55
Q

factors affecting the radiographic image (6)

A

the animal
FFD
distortion
detail
density
contrast

56
Q

high opacity

A

bone; absorb most of xray causing less to reach exposed film

57
Q

low opacity

A

lungs; allow more X-rays through to exposed film

58
Q

5 opacity levels

A

gas (black)
fat (dark gray)
soft tissue and fluid (gray)
bone (light gray - white)
metal (bright white)

59
Q

focal film distance (FFD)

A

between focal spot and film; more space = weaker beam

60
Q

distortion

A

masking of an objects true shape; closer to tube will be larger - closer to film and table will be more detailed and true to size

61
Q

object film distance (OFD)

A

distance from object to film

62
Q

detail

A

visual quality of radiograph

63
Q

factors affecting detail

A

focal spot size
film and screens
patient motion
tube motion
film fog/scatter radiation
distortion

64
Q

density

A

mAs; blackness in the film

65
Q

short scale contrast

A

bone; mainly black and white

66
Q

long scale contrast

A

soft tissue; black and white with more shades of gray

67
Q

when an xray beam has a high KVP or penetrating power

A

there is less difference in the absorption of the beam by tissues of different opacities

68
Q

collimator

A

determines area of exposure

69
Q

cones

A

restricts the primary beam as it comes out of machine

70
Q

filters

A

absorb the lower energy xrays that could not penetrate the patient to expose the film but may still interact with the patients tissues and cause damage or scatter radiation

71
Q

grids

A

lead strips that prevent scatter radiation from reaching the film - like a magnet

72
Q

grid cut off

A

grid isn’t lined up properly and absorbs rays that you wanted to reach the film

73
Q

causes of grid cut off

A
  • parallel grid
  • not centering grid to the primary beam
  • using incorrect FFD
  • placing temporary grid upside down
74
Q

parallel grids

A

contain strips that are arranged in a parallel fashion

75
Q

focused grids

A

contains lead strips that are placed at angles to correspond with the angles go the xray beam

76
Q

cross hatch grids

A

two sets of parallel lead strips run perpendicular to each other

77
Q

temporary grid

A

taped or attached to cassette independently

vtt 112 - diagnostic imaging (9 decks)

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