CT stuff to know

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CT stuff to know
2013-01-22 19:57:06
CT course

CBC Winter
Show Answers:

  1. in a pt coordinating system the z-axis is what?
    head to toe
  2. In a pt coordinating system the x-axis is what?
    right to left
  3. In a pt coordinating system the y-axis is what?
    anterior to posterior
  4. Pixel size = fov divided by?
    matrix size
  5. If FOV decreases without a change in matrix size then what happens?
    pixel size will decrease as well
  6. Digitization consists of 3 steps...
    scan, sample & quatize
  7. Bone is white which is what number on a gray level?
  8. Black is air and is what number on a gray level?
  9. 5 fundamentals of digitizing images are:
    enhancement, restoration, analysis, compression, synthesis
  10. Image enhancement does what?
    makes image more pleasing to the eye
  11. Image Restoration does what?
    improves quality of images that have distortions
  12. Image analysis does what?
    allows measurements and statistics to be performed as well as image segmentation (3D)
  13. Image Compression does what?
    reduces the size of the image to decrease transmission time & reduce storage space
  14. 2 types of image compression are
    Lossless & Lossy
  15. Lossless AKA?
    • Reversible
    • No loss of info
    • has a ratio of 8:1 or less
  16. Lossy AKA?
    • Irreversible
    • Some info is lost forever
    • can have ratio above 8:1 
    • Is not clinically used
  17. Image synthesis does what?
    creates images from other images or non-image data.  (ex is reconstruction techniques)
  18. in Hounsfield Units Air is what?
    Black -1000
  19. In HU Water is what?
  20. In HU scale Bone is what?
    White +1000
  21. Transformation is what?
    A lossless step, image is transformed from gray scale values in spatial domain to coefficients in some other domain
  22. 3D visualization Techniques consist of?
    Surface Rendering & Volume Rendering
  23. Surface rendering?
    • part of 3D visualization technique
    • simple procedure
    • surface of an object is created using contour data and shading the pixels to provide the illusion of depth (10% of data in 3Dspace)
  24. Volume Rendering?
    • part of 3D techniques
    • Much more sophisticated than Surface
    • used all data in 3Dspace to provide additional info.
    • Allows observer to view more details inside the object
  25. Attenuation depends on
    electrons per gram, atomic #, tissue density & radiation used
  26. Displayed FOV can be what compared to the scanned FOV?
    Less than or equal to