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image production and evaluation Semester 2 > fluoroscopy and technique FINAL > Flashcards

fluoroscopy and technique FINAL Flashcards

1
Q

who discovered fluoroscopy

A

Roentgen noticed fingers moving, but thomas edison is credited for inventing fluoro

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2
Q

what equipment makes up the fluoro machine

A

xray tube, image intensifier, C-arm, carriage

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3
Q

C-arm

A

allows the IR to be raised and lowered

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4
Q

carriage

A

the arm that supports the equipment suspended over the table

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5
Q

Image intesification tube

A

makes the image brighter so we don’t need the dark adaptation

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6
Q

brightness control

A

regulates tube mA

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7
Q

tube shutters

A

control colimation

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8
Q

how much mA is used for fluoro

A

less than 5 mA (0.5-5.0)

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9
Q

what’s the biggest advantage of image intensified fluoroscopy over earlier fluoroscopy?

A

increased image brightness due to the image intensifier

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10
Q

brightness depends on what?

A

anatomy, kV, and mA

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11
Q

ABC =

A

automatic brightness control

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12
Q

ABC

A

just like phototiming

varies the kVp and mA automatically according to subject contrast and density

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13
Q

What is ABC also called

A

ADC - automatic dose control

ABS - automatic brightness stabilization

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14
Q

the fluorescent screen is filled with?

A

cesium iodide crystals

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15
Q

image intensifying tube contains

A

cathode, anode, fluorescent screen, input phosphor screen, cesium iodide crystals

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16
Q

fluorescent screen

A

absorbs the xray photons and emits light photons

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17
Q

photocathode

A

absorbs light photons and emits electrons

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18
Q

electrostatic lenses

A

used to accelerate and focus the electrons

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19
Q

output screen

A

absorbs the electrons and emits light photons

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20
Q

input phosphor screen

A

absorbs 2/3 incident beam by producing good conversion efficiency

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21
Q

photoemission

A

the emission of electrons when stimulated by light

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22
Q

what is the output screen made of

A

cadmium sulfide

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23
Q

flux gain

A 
the ratio of the number of light photons at the output phosphor to the number of light photons from the input phosphor 
#of output light photons/#of input light photons
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24
Q

minification gain

A

when the amount of electrons that were produced at the large input screen are being compressed into the area of the small output screen
ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor.
disquared /dOsquared
makes the image brighter

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25
Q

the increased illumination of the image is due to 2 factors

A
  1. flux gain

2. minification gain

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26
Q

brightness gain

A

the ability of the I.I. to increase the illumination level of the image
brightness gain = minification gain * flux gain

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27
Q

as the intensifier ages….

A

patient dose increases

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28
Q

conversion factor

A

the illumination intensity at the output phosphor compared to the radiation intensity incident on the input phosphor
conversion factor = output phosphor illumination/input exposure rate

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29
Q

magnification

A

by increasing the voltage on the electrostatic lenses the electrons are focused at a point closer tot eh input screen causing the image to be magnified.
magnification = input screen diameter/input screen diameter used during magnification

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30
Q

magnification mode results in?

A

better spatial resolution
better contrast resolution
higher patient dose

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31
Q

veil glare

A

when the intensely bright light floods the eye

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32
Q

vignetting

A

a reduction in brightness at the edges of an image

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33
Q

pincushion effect

A

distortion of lines which curve inward at the edges of the output screen

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34
Q

viewing systems

A

systems to deliver the image from the output screen to teh viewer
some are real time, some are static

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35
Q

types of viewing systems

A

digital
video
cine
spot imaging

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36
Q

video viewing

A

includes video camera attached to the I.I tube

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37
Q

types of camera tubes

A
  1. vidicon
  2. plumbicon
  3. CCD charge coupled device
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38
Q

what types of camera tubes are used most often?

A

vidicon and plumbicon

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39
Q

video camera tube elements

A

cathode
electrostatic grids
electron gun
target assembly (anode)

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40
Q

Electron gun

A

a heated filament that supplies constant electron current by thermionic emission

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41
Q

control grids

A

form electrons into an electron beam and help to accelerate the electrons to the anode
ACTS AS A FOCUSING CUP

42
Q

accelerator grids

A

electrostatic grids that also aid in accelerating and focusing the electron beam

43
Q

3 layers of the target

A
  1. glass face plate (outside layer/window)
  2. signal plate (creates video signal)
  3. photoconductive layer (target plate) emits electrons when hit with light
44
Q

CCD

A

charge coupled devices
device that converts visible light into an electric charge
like a computer chip

45
Q

2 methods used to couple the camera to the I.I tube

A
  1. fiber optics

2. lens system

46
Q

fiber optics

A

bundles of extremely small light conducting cables

47
Q

advantages of fiber optics

A

compact

very durable

48
Q

disadvantages of fiber optics

A

cant accommodate cine/spot films

49
Q

lens system

A

accepts the light from output phosphor and converts into beam

50
Q

lens system advantages

A

allows Rad to view image while its being recorded

51
Q

lens system disadvantages

A

much larger than fiber optics and more delicate

52
Q

TV monitor

A

video signal from the tv camera is transmitted by cable to the tv monitor
the signal is then transformed into a visible image

53
Q

parts of the tv monitor

A

tv picture tube

cathode ray tube

54
Q

tv picture tube consists of

A

glass envelope
electron gun (cathode)
external coils
anode

55
Q

tv picture tube

A

the monitor creates an image as the gun sprays a stream of electrons from the camera onto screen phosphor

56
Q

active sweep

A

the first sweep in the upper left corner of the screen and moves across almost horizontally

57
Q

horizontal retrace sweep

A

the second sweep the beam returns to the left side of the screen to a point slightly below the first line

58
Q

interlacing

A

the scanning beam does a vertical retrace and repeats the entire sweeping pattern, however the lines are placed between the first set of lines

59
Q

raster

A

the horizontal linear pattern

60
Q

the entire 525 line raster pattern is scanned every

A

1/30 of a second

61
Q

the frame rate is

A

30 times per second

62
Q

each frame is

A

33ms long

63
Q

HDTV

A

has better detail and 1050 scan lines opposed to 525

64
Q

cine

A

highest dose to the patient

used mostly in cardiac studies

65
Q

what is the weakest link in the I.I. fluoro

A

the TV monitor

66
Q

quantum mottle

A

blotchy or grainy appearance caused by insufficient radiation to create a uniform image

67
Q

what is the most common solution for quantum mottle

A

to increase the fluoro tube mA

68
Q

audible alarm

A

in the U.S federal law requires an audible alarm at 5 minutes

69
Q

Minimum source to skin distance in stationary fluoro

A

15 inches

70
Q

minimum source to skin distance in mobile fluoro

A

12 inches

71
Q

tabletop exposure rate should not exceed

A

10 R/min

72
Q

lead apron and gloves

A

0.25 mm Pb/eq

73
Q

a single step away from the table

A

decreases exposure exponentially

74
Q

who’s responsibility is it to inform others to wear a lead apron?

A

the radiographer

75
Q

body habitus

A

sthenic
hyposthenic
hypersthenic
asthenic

76
Q

soft tissue

A

use lower kVp because radioluscent tissue needs less xrays

77
Q

extremities

A

low kVp because body part is thin

78
Q

radiopaque tissue

A

absorbs x rays so it needs more

79
Q

when the image requires less density

A

the mAs should be decreased

80
Q

pathology can be

A 
destructive 
constructive (additive)
81
Q

Destructive (more radioluscent)

A 
more easy to penetrate must decrease technique
metastases
emphysema
pneumothorax
osteoporosis
paget's disease
82
Q

constructive/additive

A 
must increase technique more difficult to penetrate 
pneumonia 
ascites
cirrhosis
congestive heart failure 
malignancy
pleural effustion
83
Q

casts and splints

A

exposure factors will change due to the material used

84
Q

fiberglass casts

A

usually do not require a change in technique

85
Q

plaster casts

A

requires an increase in exposure factors

86
Q

rule of thumb for casts

A

double the mAs for dry casts and triple for wet

87
Q

position

A

the position determines how much tissue you will be penetrating
a lateral chest requires more than an AP chest

88
Q

if you position a lateral ankle will you increase or decrease technique from the AP?

A

decrease because less to go through

89
Q

OD is controlled by two factors

A
  1. mAs

2. SID

90
Q

to change the density of the image you must change the

A

mAs

91
Q

to change the contrast of the image you must change the

A

kVp

92
Q

for every increase of 4-5 cm of part thickness the mAs should be

A

doubled

15% rule

93
Q

for every decrease of 4-5 cm of part thickness the mAs should be

A

halved

15% rule

94
Q

high contrast =

A

short scale black and white

obtained using low kVp

95
Q

low contrast =

A

long scale many shades of gray

obtained using high kvp

96
Q

advantages of technique charts

A

consistency in exposure from one tech to another

comparison of exams on the same pt. on different dates with different techs.

97
Q

variable kVp chart

A 
uses a fixed mAs 
kVp varies according to the thickness of the part 
usually short scale 
higher pt. dose
less exposure latitude
measurement of part is critical
98
Q

fixed kVp chart

A 
utilizes exposures that produce radiograps with a longer scale of contrast 
for each part there is an optimum kVp 
usually higher kVp than variable 
lower pt dose 
more consistency of exposures
greater latitude 
measurement not as critical
99
Q

exposure rates for age 0-5

A

when setting techniques for children use 25% of the mAs you would use on an adult

100
Q

exposure rates for age 6-12

A

use 50% of the mAs you would on an adult

101
Q

AEC

A

uses a device to sense the amount of radiation falling on the IR
the radiation exposure is terminated when enough xrays have reached the IR to produce proper OD

102
Q

if the AEC fails

A

secondary safety circuit terminates at 600 mAs

image production and evaluation Semester 2 (4 decks)

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