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Fluoro and angio > week 8 > Flashcards

week 8 Flashcards

1
Q

factors affecting fluoroscopic image quality

A
  1. contrast
  2. noise
  3. sharpness
  4. distortion
  5. temporal resolution
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2
Q

how can image contrast be improved

A
  • use of exogenous contrast agents
  • radio-opaque makers on instruments
  • high exposure rates
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3
Q

how can noise be improved

A

using higher frame rate

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4
Q

what is sharpness influenced by in II

A
  • display matrix
  • focal spot size
  • image noise
  • motion
  • FOV (or geometric magnification)
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5
Q

what is sharpness in FPD dependent on

A
  • display matrix
  • focal spot size
  • image noise
  • motion
  • pixel size of receptor
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6
Q

types of image distortion/ artifacts in a cathode ray tube (CRT) TV monitor (Vidicon/Plumbicon)

A
  1. veiling glare
  2. vignetting
  3. blooming
  4. pincushion distortion
  5. S distortion
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7
Q

daily QC by the radiographers

A
  1. visual check
  2. functional checks - fluoroscopic unit and other accessories equipment
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8
Q

weekly routine QC check by radiographers

A
  • top up consumables
  • cleanliness of the storage compartment
  • storage devices load
  • removal of stored data to clear the worklist on equipment
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9
Q

2 non vascular interventional radiology procedures

A
  1. biopsy
    - FNAC and Tru Cut Core
  2. Drainages
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10
Q

risk of FNAC

A

seeding tumours

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11
Q

patient preparation for drainages

A
  • fasting for at least 6 hours
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12
Q

history of fluoro

A
  • Whilhelm Conrad Roentgen
  • 8 nov 1895
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13
Q

primary function of fluoro

A
  • live display anatomy
  • dynamic motion/ process
  • interventional procedures
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14
Q

oldest device used for fluoroscopy

A

cryptoscope

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15
Q

effective dose of a barium enema procedure

A

3-6mSv

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16
Q

xray vs fluoro

A

xray
- high mA, low second
- high SNR
- low temporal resolution

fluoro
- low mA, variable second
- low SNR
- high temporal resolution

17
Q

how does frame averaging affect image quality

A

frame averaging = decrease noise = decrease temporal resolution

18
Q

components of a conventional fluoroscopic unit

A
  • high voltage generator
  • xray tube
  • xray image receiver: II
  • viewing system
19
Q

undercouch fluoroscopy meant that detector is

A

on top

20
Q

components of the II

A
  • input phosphor layer
  • photocathode
  • focusing electrode
  • vacuum enclosure
  • anode
  • output phosphor layer
21
Q

what does the input phosphor layer consist of

A

cesium iodide (CsI) crystals
- prevent lateral light spread
- for scintillation

22
Q

what is the function of the photocathode

A
  • converts light photon to photoelectron
  • efficiency 20%
23
Q

what is the output phosphor layer made of

A

thin powdered phosphor

24
Q

what does the output phosphor layer do

A

converts photoelectron back to light photon

25
Q

how many electron corresponds to how many light photons

A

1 electron = 200 light photons

26
Q

what is the formula for brightness gain

A

minification gain x electronic gain

27
Q

how is geometric magnification achieved

A

selecting smaller central portion of the input phosphor to project onto the output phosphor

28
Q

what does magnified image compromise

A

noise becomes more prominent –> reduced SNR

  • solution is to increase air kerma = increase radiation dose
29
Q

what is automatic brightness control for

A

to prevent fluctuation in
- brightness image
- SNR

30
Q

major component in an optical system

A
  • collimating lens
  • aperture
  • focusing lens
31
Q

what is the function of the optics camera system

A

captures and converts light photons to analogue electrical signals

32
Q

what in the conventional fluoroscopic system is combined to form a FPD

A
  • II
  • optical lens
  • camera
  • analog processing & A/D
  • video camera
  • cine camera
33
Q

pros of II

A
  • better low noise performance
34
Q

cons of II

A
  • big and bulky
  • risk of image distortions
35
Q

pros of FPD

A
  • less bulky
  • absence of image distortions
  • broaden applications
36
Q

cons for FPD

A
  • high electronic noise at “low noise level range” compared to II

Fluoro and angio (9 decks)

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