RT 265 Digital Radiography

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  1. What is a Pixel?
    (picture element)  This is the Basic component of the digital image; What we see in 2D
  2. What is a Voxel?
    • Volume Element. This is the 3D element that includes Depth.
    • The pixel is essentially the End of the Voxel
  3. Voxel is the ------- of the patient?
    Thickness of the patient
  4. Is Voxel controlable in CR or DR?
    No... its fixed in CR and DR

    • With large patients =Poor image
    • vs
    • Small patietn= better image
  5. What is a Matrix?
    • The ACTUAL Image we SEE is made up of a series of Pixels in Rows & Colums called a
    • Matrix
  6. What is a BIT?
    A BIT is the amount of GRAY SCALE in the image.  (Contrast) More bits=more shades of gray

    • (bit is the exponenet to TWO)
    • 2Bit is two to the second or four
    • 2squared 2(2) = 4 shades of gray displayed

    Today most image are 10 to 12 Bits
  7. What is FoV?
    • Field of View.
    • How much anatomy is Displayed

    12cm FoV display 12cm of anatomy on the screen

    The Smaller FoV= More Magnified Anatomy
  8. Small FoV = Better or Worse Spatial resolution

    (This is true for all modalities Except for DR)
    Smaller FoV= Better Spatial Resolution

    but, image will appear larger

    8x10= sharper image vs 14x17=less sharp
  9. Singal=
    Singal =Photons
  10. Noise=
    Noise= Scatter radiation
  11. Window Width
    The GRAY SCALE of the digital image.
  12. Larger Window width=
    More or less grays scales?
    Larger Window Width= MORE Gray scales=Lower contrast

    (narrow Width= fewer gray scales-shades of gray)= Higher contrast

  13. Window Level=
    • Window Level is the DENSITY or BRightness of the image.
    • The Higher the number the Brighter the image
  14. What is the Photoconductor made up of?
    Amorphous Selenium-->captures x-ray photon & generates a signal
  15. Inderect (CR) Intensifying Screen is made up of?
    Cesium-iodide crystals & the Photocondector is made up of Amorphous silicon
  16. What are the Elements of DRD Imaging system
    1. Capture Element-to capture x-ray photon

    2. Coupling element-Transfers x-ray generated signal to the collection element

    • 3. Collection Element- Photodiode, CCD, TFT, CMOS-(light sensitive devices that collect light photons)
    • TFT-collect Electrons
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RT 265 Digital Radiography
2012-09-10 01:21:21

RT 265 Digital lecture 1 Fall 2012
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