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Dose Limits for Ionizing Radiation > Fluoroscopy week 3 > Flashcards

Fluoroscopy week 3 Flashcards

1
Q

Fluoro is what type of exam

A

Dynamic Radiographic

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2
Q

Fluoro involves _ during the exam

A

active diagnosis

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3
Q

Fluoro is primarily the domain of the

A

Radiologist

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4
Q

Radiographers should perform fluoroscope only for _ examinations

A

static

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5
Q

Fluoro was invention is credited to _ and when

A

Edison in 1896

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6
Q

Fluoroscopic screen consists of a

A

specialized x-ray tube with an image receptor

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7
Q

What was held by hand and put in front of the patient and x-ray tube (1st Fluoro)

A

a viewing hood

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8
Q

when was image intensification tubes were developed in

A

1948

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9
Q

what allow to view safely

A

digital monitoring system

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10
Q

Fluoro is currently used only for studies that require

A

observation of dynamic physiological function
ex-. the flow of barium through the GI tract
ex.2- injection of a contrast medium into the heart

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11
Q

what is the arm that supports the equipment suspended over the table

A

carriage

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12
Q

the carriage includes an

A

image intensification tube

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13
Q

what is the image intensifier

A

increases the brightness

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14
Q

in order to gain access the the patient what can be done

A

the carriage can be disengaged and pushed away

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15
Q

exposure cannot continue until the

A

the carriage is returned and locked into position

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16
Q

Fluoroscopic x-ray tubes are very similar to what

A

Diagnostic tubes

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17
Q

Fluoroscopic x-ray tubes are different from diagnostic tubes how

A

they are designed to operate for longer periods of time at much lower mA

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18
Q

4 parts of a fluoro system

A
  1. II
  2. tube
  3. carriage or gantry
  4. monitor
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19
Q

what is the Fluoroscopic mA range is

A

0.5-5.0 mA

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20
Q

Fluoroscopic tubes are equipped with

A

electrically controlled shutters

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21
Q

Fluoro tubes are equipped with electrically controlled shutters that permit _ both Fluoro and spot imaging

A

maintenance of close collimation from the Fluoro carriage

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22
Q

Early Fluoroscopic screens were

A

very dim

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23
Q

what is dark adaptation

A

a procedure in which light levels are reduced for a pd. of at least 10-15 min

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24
Q

Dark adaptation, why are the light levels are reduced for a pd. of at least 10-15 min.

A

to permit the rods of the eye to become activated

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25
Q

The brightness of the fluoro image was not raided to daylight levels until

A

image intensification technology was developed in 1948

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26
Q

an image intensification tube is designed to

A

electronically amplify the brightness of an image

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27
Q

modern image intensifiers are capable of increasing image brightness _ times

A

500-8,000

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28
Q

The primary x-ray beam exits the patient and strikes the

A

input screen of the II tube

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29
Q

what is the image intensifier tube

A

vacuum tube w.a cathode and an anode

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30
Q

fluorescent screen is an

A

input screen

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31
Q

The fluorescent screen absorbs

A

the x-ray photons and emits light photons

32
Q

photocathode is a

A

cathode of the tube

33
Q

the photocathode absorbs

A

the light photons and emits electrons

34
Q

electrons are accelerated from the

A

cathode to anode

35
Q

the same time the electron beam is focused onto the

A

output screen, which is much smaller than the input screen

36
Q

what are electrostatic lenses used for

A

to accelerate and focus the electrons

37
Q

The primaryBRIGHTNESS GAIN occurs from the

A

acceleration and focusing of the electron beam

38
Q

The output screen absorbs the _ and emits

A

electrons

light photons

39
Q

viewed on

A

video monitor

40
Q

The input screen consists of

A

0.1 - 0.2 mm layer of sodium-activated cesium iodide (Csl) phosphors

41
Q

For the input screen, the sodium-activated cesium (CsI) phosphors coated onto the

A

concave surface of the II tube

42
Q

the surface of the II tube of the input screen may be made of _ and ranges from

A 
glass
titanium, 
steel
aluminum
6" - 23" in diameter
43
Q

the screen is

A

concave

44
Q

The cesium iodide (CsL) phosphors are packed together very tightly so they absorb about _ of _ producing a good

A

66% of the incident beam

conversion efficiency or quantum yield

45
Q

What is applied to the input screen to prevent a chemical interaction with the photocathode

A

extremely thin protective coating

46
Q

the photo emissive materials absorb the light photons and emit electrons in a process called

A

photoemission

47
Q

what are electrostatic lenses

A

series of charged electrodes located inside the glass envelope of the tube

48
Q

the electrons are

A

negative

49
Q

what reverses the image so the output screen image is reversed from the input screen image

A

focal point

50
Q

The focal point reverses the image so the output screen image is

A

reversed from the input screen image

51
Q

Image intensification tubes can be designed to magnify

A

the image electronically by changing the voltage on the electrostatic lenses

52
Q

By changing the voltage on the electrostatic lenses they are know by these 4 types of intensifier fields

A

multi-field
dual-field
triple field
quad-field

53
Q

magnification image intensifiers are capable of _ magnification

A

1.5 -4x

54
Q

The magnification image intensifiers are controlled at the

A

fluoro carriage

55
Q

The mag factor is calculated as

A

Magnification= input screen diameter/
diameter if input screen
used during magnification

56
Q

The anode is _ charged and is normally supplied with about

A

+

25 kV

57
Q

This charge causes a tremendous attraction of the

A

negative electrons from the photocathode

58
Q

The anode is positioned inside the

A

glass envelope

59
Q

electrons pass through the

A

anode field and onto the output screen

60
Q

The output screen is also a _.

A

fluorescent screen

61
Q

The output screen consists of

A

silver-activated zinc-cadmium sulfide phosphor

62
Q

the electrons that strike the screen are converted into

A

green light photons that exit the tube

63
Q

what transmit the image some distance without loss of resolution

A

fiber optics

64
Q

what is a measurement of the increase in image intensity achieved by an image intensification tube

A

total Brightness Gain

65
Q

The total brightness gain is determined by 2 factors

A

minification gain

flux gain

66
Q

Minification gain occurs as a result of the

A

same number of electrons that were produced at the large input screen being compressed into the area of the sm. output screen

67
Q

out put screens, most are how big

A

6” or 9”

68
Q

typical output screens are

A

1” in diameter

69
Q

Minification gains formula

A

Minification gain=input screen diameter2

output screen diameter2

70
Q

minification gain is simply an _

not an improvement in the quality or # of photons making up the image

A

increase in brightness/intensity

71
Q

Photocathode converts

A

photon to electrons

72
Q

The Flux Gain is a measurement of the

A

increase in light photons due to the conversion efficiency of the output screen

73
Q

Flux gain does not take into account the

A

conversion efficiency of the input screen

74
Q

The flux Gain only deals with the _ and is accomplished by the

A

gain

electron to light conversion at the output screen

75
Q

total brightness gain formula

A

brightness gain=minification gain x flux gain

76
Q

Brightness gain deteriorates as much as _ per year because the

A

10%

input and output screen phosphors age

Dose Limits for Ionizing Radiation (16 decks)

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