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Exposures II > Chapter 33: Fluoroscopy > Flashcards

Chapter 33: Fluoroscopy Flashcards

1
Q

who was the fluoroscope invented by and when

A

Thomas Edison in 1896

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2
Q

where is the xray tube and image intensifier loacted in fluoro

A

xray tube is below table and image intensifier is on top

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3
Q

dynamic imaging modality designed to observe moving structures in the body

A

Fluoroscopy

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4
Q

what should the SSD be for mobile equipment

A

30 cm (12 inches)

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5
Q

what should the SSD be for fixed fluoroscopic

A

38 cm (15inches)

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6
Q

What is the mA range for the fluoroscopic xray tube

A

0.5 to 5 mA

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7
Q

purpose of the image itensification

A

increase brightness of fluoroscopic images by thousands (8,000 times)

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8
Q

Electronic devise mounted above the table and patient and permantely attched to the xray tube

A

Image Intensifier

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9
Q

components of the image intensifier

A

Input phosphor
photocathode
electrostatic lenses
anode
output phosphor

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10
Q

Function of the input phosphor

A

converts xray photons to light photons

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11
Q

coated with cesium iodide

A

Input phosphor

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12
Q

*concave surface
*approx. 10-35 cm in diameter
*coated with cesium iodide
* converts xray photons to light photons

A

input phosphor

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13
Q

made of cesium antimony

A

photocathode

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14
Q

function of photocathode

A

converts light photons to electrons ; called photoemission

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15
Q

Mimics the pattern of light demonstrating the anatomy of the patient emitted by the input phosphor (latent image)

A

Photocathode

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16
Q

narrowing the electron beam

A

electrostatic lenses

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17
Q

very high exposures directly into :

A

eyes, neck, hands

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18
Q

*positively charged end of the image intensifier
*attracts the photoelectrons due to elctrostatic charger
*contains the output phosphor at end

A

Anode

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19
Q

function of the elctrostatic lenses :

A

accelerate and focus the electrons toward the output phosophor

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20
Q

made of zinc cadmium
sulfide
glass fluorescent screen

A

Output phosphor

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21
Q

function of the output phosphor

A

Converts photoelectrons to visible light

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22
Q

what type of diagnosis is fluoroscopy

A

Active

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23
Q

what type of examination is fluoroscopy

A

Dynamic

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24
Q

image intensification tubes dveleoped in 1948. there was mirror optics for viewing what was that replaced with

A

replaced with closed circuit TV systems

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25
Q

fluoroscopic uses for functional studies:

A

o Gastrointestinal (GI) tract studies
o Angiograms
o Line placements
o Orthopedic surgeries

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26
Q

total brightness gain

A

minification gain * flux gain

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27
Q

o 0.1–0.2 mm layer of sodium activated cesium iodide (CsI)
o Converts intercepted x-ray beam to light

A

Input screen

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28
Q

Emits electrons when struck by light emitted by input screen

A

Photocathode

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29
Q

audible timer, radiation protection

A

five minute timer

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30
Q

where should the patient be shielded

A

from behind since the xray tube is below

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31
Q

what is the last image hold for

A

to decrease dose
pt. protection

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32
Q

measurment of the increase in image brightness due to the conversions of energy in the image intensifier

A

Total brightness gain

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33
Q
  • Accelerate and focus electron pattern across tube
    to anode
    *primary source of brightness gain (due to acceleration of electron stream and increased kinetic energy)
A

electrostatic lenses

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34
Q

what is increased in magnification mode

A

increased resolution
increased patient dose

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35
Q

magnification =

A

input screen diamter/ diamater of input screen used during magnification

36
Q

distortion in fluoro

A

vignetting

37
Q

where is the focal point in magmode

A

focal point closer to input phosphor in magmode

38
Q

what size surface area is during magmode

A

smaller surface area

39
Q

measurement of increased image intensity achieved by image intensifier

A

Brightness gain

40
Q

results from concentration of large electron volume from input phosphor, being focused down onto small area of output phosphor

A

Minfication gain

41
Q

input over output

A

minification gain

42
Q

measurement of conversion efficiently of output screen

A

Flug gain

43
Q

Automatically adjusting the contrast , takes account the thickness

A

Automatic Brightness control

44
Q

help to see in bright lights, phototopic

A

Cones

45
Q

help to see in low light, scotopic

A

rods

46
Q

is input or output bigger

A

input is bigger vs. output

47
Q

how much lead is in the bucky slot cover

A

0.25 mm

48
Q

how much lead is in the curtain

A

0.25mm

49
Q

how much lead is in the lead aprons

A

0.25mm

50
Q

how much lead is in the lead aprons in fluoro

A

0.5mm

51
Q

image intensification was introduced in 1948. What was modified.

A

-higher visual acuity
-uses photopic vision (cones)
-reduced fluoroscopic dose

52
Q

Image intensification tube components:

A

-input screen and photocathode
-electrostatic lenses
-magnification tubes
-anode and output screen
-total brightness gain (minification gain * flux gain)

53
Q

what does greater voltage to electrostatic lenses do

A

-increases acceleration of electrons
-shifts focal point away from anode

54
Q

hole in center allows electrons to pass through to output screen

A

Anode

55
Q

Results from concentration of large electron volume from input phosphor, being focused down onto small area of output phosphor

A

Minification gain

56
Q

minification gain =

A

input screen diameter ^2/output screen diameter^2

57
Q

Measurement of conversion efficiency of output screen
ex. one electron strikes output screen
-50 light photons emitted per electron striking output phosphor
-flug gain 50

A

Flux gain

58
Q

Image quality

A

Contrast, resolution, distortion, quantum mottle

59
Q

-controlled by amplitude of video signal
-digital systems use post processing
(window width and filtering algorithm)
Affected by:
-scattered ionizing radiation
-penumbral light scatter

A

Contrast

60
Q

Which is better?
Fluoroscopic or static radiography resolution

A

Static radiography

61
Q

Resolution varies depending on geometric Factors:

A

SID, OID, minification gain
longer sid, smaller oid

62
Q

Edges of image intensifier have lower resolution due to:

A

Vignetting

63
Q

Automatically adjusting the contrast
takes account of the thickness

A

Automatic brightness control

64
Q

penumbra

A

unsharpness

65
Q

numbra

A

sharpness

66
Q

What does more scatter do to the contrast

A

Decrease contrast

67
Q

Size distortion

A

-affected by same parameters as static radiography (primarily oid)
- geometric problems in shape of image intensifier input screen
-concave shape helps reduce distortion
-vignetting or pincushion effect
-not a problem with TFT matrices
-uniform resolution across flat panel detector array

68
Q

blotchy, grainy appearance
-caused by too little exposure
-most commonly remedied by increases mA

A

Quantum Mottle

69
Q

Improved by increasing total exposure to intensifier input phosphor
-increase mA
-reduce distance between patient and image intensifier
-increase kvp

A

Quantum Mottle

70
Q

Most common viewing system:

A

Video
-video camera attched to output phosphor
-fluoro video camera uses CCD
-display monitor for viewing

71
Q

Highest energy scatter

A

-90 degrees angle to incident beam
- same level as radiographer / radiologists gonads

72
Q

What is the difference with flat panel fluoroscopy ?

A

-No intensifier tube
-no vignetting
-no dose increase in mag mode

73
Q

C- arm fluoroscopic units

A
  • populary for surgery, er, orthopedic studies
  • operates the same as stationary units
    -pary particular attention to radiation dose when using mobile fluoroscopy
74
Q

what generator is used for digital fluoroscopy

A

High power generator

75
Q

in digital, Image intensifier output screen coupled to :

A

TFT

76
Q

in digital fluoroscopy, what is connected to each pixel

A

Photodiodes

77
Q

what is used in digital fluoroscopy to lower noise

A

pixel binning

78
Q

Use C C D to generate electronic signal
Signal sent to A D C
Allows for post-processing and electronic storage and distribution
Last image hold function
Post-exposure image processing

A

digital fluoroscopy

79
Q

patient protection for fluoroscopy

A

-audible alarm at 5 minutes
-same rules for collimation
-last image hold

80
Q

how much aluminum for filtration for fluoro

A

2.5mm

81
Q

how often should the fluoro system and lead aprons be checked

A

the fluoro system should be checked every 6 months
the lead gowns should be checked yearly

82
Q

What is the mR for xray tube and fluoro

A

Xray tube = 100mR
fluoro= 10mR

83
Q

purpose of intensifier tube :

A

To increase image brightness

84
Q

-converts xray to photons
-cesium iodide

A

Input phosphor

85
Q

-converts light to photons to electrons
-cesium and antimony

A

Photocathode

86
Q

-focuses the photoelectrons to the output phosphor
25-35kvp
-located on the inside of the image intensifier

A

Electrostatic lenses

Exposures II (7 decks)

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