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RAD413 > fluoroscopic system: flat panel (modern) > Flashcards

fluoroscopic system: flat panel (modern) Flashcards

1
Q

what is the difference between the production of xrays in flat panel and image intensifier fluroscopu

A

flat panel = receives xrays from high spec medium frequency generator

image intensifier = receives xrays from regular xray tube

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2
Q

what is the power range of the frequency generator in flat panel fluroscopy

A

65-126kw

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3
Q

what is the exposure range of the xrays the frequency generator makes for static images and fluroscopy

A

static imaging = 40-150kV, 32-63mA

Fluroscopy = 40-125kV, 0.5-4mA

both have 5ms-5 second times

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4
Q

what is the range of pulsed images per second the can be produced by the frequency generator

A

1 - 8 per second

(cardiac systems up to 30/sec)

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5
Q

describe the process of how a flat panel fluoroscopic system works

A
  1. xrays converted to light using caesium iodide in a scintillator

(no electron acceleration or minification to reduce noise)

  1. light then reaches a low-noise amorphous silicon (a-Si) photodiode array where it is converted into an electrical charge
  2. Each photodiode represents a single pixel, and each produces an electrical charge that is read out digitally by the TFT array layer underneath
  3. then finally being sent to the image processor
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6
Q

why is the caesium iodide layer thicker in flat panel than image intensifier system

A

for greater xray absorption/sensitivity

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7
Q

flat panel does not have electron acceleration to minimise noise production, so what does it do instead to reduce noise

A

pixel binning

  • adding together groups of pixels to make a smoother image
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8
Q

what is a negative of pixel binning

A

reduced resolution

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9
Q

how can pixel binning affect frame rate

A

increase/faster frame rates as it reduces the amount of data to be handled

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10
Q

what are the 2 ways to magnify an image using the flat panel system

A
  1. electronic zoom of binned pixels (no increase in resolution, just part of panel is displayed magnified
  2. pixels unbanned in centre of detector, increases resolution
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11
Q

both fluroscopy and recorded images are dynamic methods

achieved nu pulsing xrays at several frames per second

A
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12
Q

what controls the xray pulses in fluroscopy

A

gridded tube, it suspends electrons ready to expose

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13
Q

compare the dosage of pulsed and continuous fluroscopy

A

pulsed fluroscopy significantly reduces dose to patient

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14
Q

pulsed fluroscopy does reduce dosage to patient however there are disadvantages associated, what are they

A
  • blurred when patient moves
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15
Q

for very slow pulse rates as in pulsed fluroscopy, when several frames have been averaged to smooth out the noise what can happen to the contrast of the imageq

A
  • have higher contrast resolution due to reduced noise
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16
Q

what is the typical fluroscopy pulse rate

A

1-15 frames per second

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17
Q

what are the 5 things you can adjust to control flat detector image quality

A
  1. ABC, AGC, AEC
  2. collimation
  3. edge-enhancement
  4. noise reduction filter
  5. pulsed imaging to reduce dose
18
Q

what are the 4 types of noise reduction filters/systems

A
  • temporal/recursive filtering / frame averaging
  • motion tracking
  • background supression
  • pixel binning
19
Q

what type of artefact/effect will you find in image intensifier but not flat panel system

A

no pin-cushion effect due to curvature of front of image intensifier causing blur at the edges

20
Q

why is there no s-distortion found in flat panel but is in image intensifior

A
  • no magnets accelerating electrons in flat panel
  • so no s-distortion caused by earths magnetic field acting on focussing electrodes
21
Q

what is done to correct s-distortion in image intensifier system

A

s-distortion corrections are made to the system by the service engineer

22
Q

what is another advantage that flat panel has over image intensifier system

A

no vignetting, where the periphery of the image is less bright than the center and has lower resolution

23
Q

know that overall the flat panel has 3 major benefits over image intensifier in terms of artefacts/errors that can occur in image production

A
  1. pin cushion effect
  2. s-distortion
  3. vignetting
24
Q

what are edge detection filters used for

A

edge enhancement

25
Q

how does the fluoroscopic machine differ from the catheter lab/ high-performance systems to regular

A
  • gantry c-arm suspended from floor or ceiling mount
26
Q

describe how the additional advantages/features found in high performance systems

A

anti-collision software, gantry and table (predictive and actual)

fast moving (moves 180 degrees in 30 seconds)

27
Q

all high performing systems use flat panel not image intensifier

A
28
Q

high performance systems have virtual collimation, what is this

A

allows you to quickly collimate or perform adjustments at the workstation right before X-ray exposure

29
Q

high performance systems have roadmapping, what is this

A

can overlay the vessel to reduce fluroscopy to check location of guide wire

30
Q

what is LIH

A

last image hold

31
Q

high performance systems have live stent enhancement, what is this

A

real-time verification of the stent positioning while moving the device.

32
Q

high performance systems can image fuse with CT, US etc

A
33
Q

what are the highest risk dose procedures in R&F and other fluoroscopic systems

A

R&F (continuous xray image) = multiple lateral images of the pelvis/lower spine

other systems = cardiac and neurological intervention

34
Q

what is the optimal distance of the patient to the tube and patient from detector

A

patient to tube distance = 80cm

patient to detector (flat panel or image intensifier) = 30cm

35
Q

why is there an optimal distance of the detector and tube from patient?

A
  • reduces the scatter pattern of the radiation to minimise risk to operator and surrounding ppl
36
Q

what is dose awareness

A

back scatter to operator when they normally work from the right

37
Q

when the c arm is lateral, where is the back scatter the highest

A

on the tube side of the patient (right beside where the x-rays are coming out of tube)

38
Q

left lateral, a common projection gives highest operator dose when operators put catheters into femoral and radial arteries

A
39
Q

what are the ranging radiation protection equipment when using fluroscopy

A
  • lead curtains/suspended drapes (mobile or suspended from table)
  • lead apron
  • lead gloves
  • lead goggles
  • lead thyroid collar
  • mask
  • lead shoes
  • lead panties
40
Q

what are some dose control activities you can do

A
  • dosimeter under lead apron, fingers or next to eyes
  • never stand within 2m of patient
  • keep fluroscopy to minimum (use it pulsed)
  • last image hold to avoid need for further xrays
  • use 2nd monitor for reference images to avoid live fluroscopy
  • store fluoroscopic images when image quality is enough
  • keep operator aware of flare time and patient dose displayed
  • keep image receptor close to patient as possible
  • dont magnify imaging unless needed
  • collimate
41
Q

greatest patient dose risk in order of different imaging:

  1. angiography system with 3D
  2. catheter lab
  3. R&F system
  4. Surgical mobiles
    5.finger xray
A
42
Q
A

RAD413 (24 decks)

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