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MED 107- MEDICAL PHYSICS II > 19. X-RAY DETECTORS: COMPUTED RADIOGRAPHY > Flashcards

19. X-RAY DETECTORS: COMPUTED RADIOGRAPHY Flashcards

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1
Q
  1. What are two examples of Indirect Systems?
A
  1. Computed Radiography Systems (CR)
  2. Indirect Digital Radiography Systems (IDR)
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2
Q
  1. What do both of these indirect systems utilise?
A
  • Cassettes
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3
Q
  1. What happens with the Cassette in Indirect Digital Radiography Systems?
A
  • the information from the cassette is directly converted
    into an X-Ray image
  • there is no intermediate step of converting the X-Rays
    into light
  • the emergent X-Rays will directly cause the system to
    produce an electrical signal
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4
Q
  1. What happens with Indirect Imaging?
A
  • the X-Rays are absorbed
  • they are then converted into light
  • they are then converted once more to an electrical
    signal
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5
Q
  1. How does the Computed Radiography System (CR) work?
A
  • this is a system that produces digital Radio-graphical
    images
  • it does this in a very similar method to Film Screen
    Technology
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6
Q
  1. What does the Computed Radiography System not generally require?
A
  • it does not require modifications to the X-Ray
    equipment
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7
Q
  1. What happens when a Computed Radiography system receives an Exposure?
A
  • the CR imaging plate retains the latent image
  • this is similar to what happens in film technology

THE DIFFERENCE OCCURS:
- when the latent image is processed
- the latent CR image is scanned using a laser beam
- it is digitised using a CR reader

WHEREAS:
- the latent image is processed chemically using film
technology

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8
Q
  1. In a Computed Radiography system, what happens to the data that was digitised using the CR Reader?
A
  • the data is sent to the computer
  • it is displayed
  • it is manipulated
  • it is archived
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9
Q
  1. What is the currently the most common imaging system?
A
  • Computer Radiography
  • that makes use of imaging plates
  • these are known as Photostimuable Phosphors (PSP)
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10
Q
  1. What do typical CR Resolutions range between?
A
  • they range from 100 to 200 µm
  • the spatial resolution is lower than that of fine or
    detailed film screen technology
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11
Q
  1. What does this image show?
A
  • it shows how the latest systems can employ multiple
    parallel lasers
  • they also have many light detectors and scanners
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12
Q
  1. What are the two main systems of Indirect Digital Radiography?
A
  1. Those based on Thin Film Transistor (TFT)
    Technology
  2. Those based on Charged Coupled Device (CDC)
    Technology

NB:
- both designs make use of phosphors and scintillators
- these produce light when exposed to X-Radiation

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13
Q
  1. What is the difference between the 2 Indirect Digital Radiography systems?
A
  • the differences revolve around how light is
    detected
  • as well as how light is converted into a useful electrical
    signal
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14
Q
  1. Do these images make sense?
A
  • yes
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15
Q
  1. What is the magnitude of the Resolution System for Indirect Digital Radiography?
A
  • 100 and 200 µm
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16
Q
  1. What are some design considerations when it comes to Charged Coupled Device Technology (CCD)?
A
  • how to connect the CCD array
  • where to place the CCD array
17
Q
  1. What happens when any X-Ray reacts with a CCD?
A
  • they create a false signal
  • this is because CCDs are sensitive to X-Rays
  • this means that the CCD array cannot be positioned in
    line with the Scintillator Crystal
  • because this is where the X-Ray rays may interact with
    it
18
Q
  1. How else can we position the CCD array to avoid
    X-Ray sensitivity based issues ?
A
  • we can use fibre optical tapers
  • we can use a mirror and an optical lens arrangement
19
Q
  1. How do the detectors in Direct Digital Radiography work?
A
  • they work in a similar way to ionisation chambers
20
Q
  1. What happens when Incident Radiation Passes into the sensitive volume?
A
  • it causes electrons to be liberated from their orbits
  • this creates positive and negative ions
  • these ions carry charge from one electrode to the
    other
  • these ions are attached to their respective electrode
  • this creates a current
21
Q
  1. What does the Image Acquisition System do?
A
  • it converts X-Rays to an electrical signal
  • it does this without the need for first converting the X-
    Rays to light
22
Q
  1. What does this image show?
A
  • a flat panel detector
  • this is the most modern form of Direct Digital
    Radiography
  • it is used with regards to fluoroscopic materials
23
Q
  1. What are the advantages of Computed Radiography (CR)?
A
  • this is an indirect mechanism
  • it has greater versatility
  • it can be used with unmodified equipment
  • it is available in different Cassette Sizes

MED 107- MEDICAL PHYSICS II (108 decks)

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