MIC Ch2 CT Image Formation

  1. 7. Using _____ reconstruction filter would decrease the apparence of noise in a CT image.
    1. no
    2. a sharp
    3. a smooth

    D. 3 only
  2. 18. A _____ scan uses only a single projection.
    1. conventional, or serial
    2. hilical
    3. localizer

    B. 3 only
  3. 15. Which of the following statements is FALSE regarding 3D SSD?

    A. The volume data, from which the 3D SSD is generated, is created by combining transverse, sagittal, and coronal reconstructions
  4. 27. Which type(s) of storage media may hold CT image data?
    1. internal hard disk
    2. CD
    3. re-writable optical disk

    C. 1, 2, and 3
  5. 28. ____ may have to be edited fom the data set to get a diagnostic MIP of a CTA exam.

    A. Bones
  6. 23. Which of the following is NOT an advantage of a helical study compaired to a conventional, serial CT study?

    A. Offers the best image quality for a brain exam
  7. 25. Which of the following utilizes convolution?
    1. 3D SSD
    2. Fourier transform
    3. filtered back projection

    A. 3 only
  8. 29. In which technique are tissues other than the surface of a structure excluded by setting a threshold value and eliminating pixels above or below that threshold?

    D. 3D shaded surface display
  9. 10. From which of the following can the most diagnostic multi-planar reconstructions be generated?
    1. stacked transverse images from a helical scan
    2. stacked transverse images from a conventional, serial scan
    3. stacked localizer images

    D. 1 only
  10. 6. The actual attenuation data measured by the detectors from all projections during a scan is contained in CT _____ data.
    1. image
    2. convolved
    3. raw

    B. 3 only
  11. 39. Which of the following is TRUE regarding the slice thickness of an image reconstructed from a helical scan?
    1. on a multi-row scanner, the thickness is equal to the beam collimation
    2. on a single-row scanner, the thickness is wqual to the beam collimation
    3. on a single-row scanner, the thickness can be varied retrospectively

    D. 2 only
  12. 4. A retrospective reconstruction, in which the reconstruction field-of-view is varied, uses:

    A. CT raw data
  13. Which of the following is common to both a localizer scan and a conventional, serial CT scan?

    A. They both produce digital images
  14. 30. Which of the following statements is TRUE?
    1. the amplified electrical signal obtained from the detectors must be digitized
    2. digital CT images are numerical representations of cross-sectional anatomy
    3. digital signals may be formed by sampling analog signals at discrete time intervals

    D. 1, 2, and 3
  15. 1. ____ is the mathematical process used by single-row detector scanners to reconstruct CT images from raw data.

    B. Filtered back projection
  16. 38. 3D shaded surface displays are performed on CT:
    1. image data
    2. raw data
    3. attenuation profiles

    C. 1 only
  17. 11. A pixel is a:

    B. Single 2D picture element within the image plane
  18. 37. The pencil thin section of the x-ray fan beam that strikes a single detector is called a:

    B. Ray
  19. 8. A kernel is a:

    B. Filter applied to the CT raw data
  20. 24. An increase in _____ does NOT occur in the resulting images when applying a sharp, or high-pass reconstruction filter during the image reconstruction of CT raw data
    1. contract resolution
    2. edge enhancement
    3. the appearance of noise

    D. 1 only
  21. 5. CTA images come from a _____ scan
    1. conventional, or serial
    2. helical
    3. localizer

    D. 2 only
  22. 13. If an image matrix has 360 rows and 360 columns, how manyu pixels are there in the image?

    A. 129,000

    a pixel is a 2-dimensional picture element defined by the rows and columns of the image matrix. f there are 360 rows and 360 columns in an image matrix, the total number of pixels in the image matrix is 360 x 360.
  23. 36. The _____ determines the intensity of the laser beam in a aser camera.
    1. intensifying grid
    2. pixel values in the image data
    3. magnifying power of the lens

    C. 2 only
  24. 21. Which of the following is a reconstuction technique applied to the raw data after the primary reconstruction has already been accomplished?

    D. Retrospective reconstruction
  25. 19. What does convolution do to the image quality when it si added to the back projection reconstruction process?

    C. Enhances important characteristics of attenuation profiles thus reducing streak and star artifacts
  26. 34. Which of the following may occur during the interscan delay of a conventional, or serial, CT scan performed on a continuous ratation scanner?
    1. the table position is incremented
    2. the tube continues to rotate in the same direction as during the scan
    3. the tube assembly makes a 360* rotation

    A. 1, 2, and 3
  27. 32. _____ allows helical data to be converted into planar raw data.

    B. Interpolation
  28. What is the most common type of film used for recording CT images?

    A. Single emulsion
  29. 16. A helical scan performed on a 64 slice MDCT scanner is reconstruction with:

    C. Cone beam reconstruction
  30. 26. _____ yields an image that appears 3D but also shoes anatomical details above and below the 3D surface.

    B. VR
  31. 2. MDCT scanners capable of collecting 64 slices in a single rotation do NOT:

    A. Use filtered back projection as their method of image reconstruction
  32. 40. MIP images:

    D. do NOT demonstrate detail beneath the brightest pixel
  33. 31. Multi-planar reconstructions are performed on which of the following?
    1. image data
    2. raw data
    3. attenuation profiles

    D. 1 only
  34. 20. The _____ move(s) during a helical scan on a third-generation scanner,.
    1. x-ray tube
    2. patient table
    3. detector elements

    B. 1, 2, and 3
  35. 17. A CT system manufacturer has a scanner in which the focal spot of the x-ray beam can move to two, slightly separated, distinct locations. What benefit does the dual focal spot provide compared to an identical scanner possessing a single focal spot?
    1. the number of projections is doubled
    2. the nubmer of rays in a single projection is doubled
    3. the patient dose is halved

    B. 1 only
  36. 35. On a third-generation single-row detector scanner, if there are 715 detectors and there are 900 projections in a full rotation how many samples of attenuation data are collected for the raw data of a single slice if the scan calls for an overscan of a 400* rotation?

    C. 715,000

    There are 900 projections in a full rotation of 360*, but the question asks about an overscan of 400*. An overscan is sometimes used to decrease aliasing artifacts. 900 projections in 360* means that there are 900 / 360, or 2.5 projections per degree. There are 400-360, or 40 more degrees than a full scan. Multiplying 40 degrees by 2.5 projections per degree yields an additional 100 projections. Therefore, the total number of projections equals 900 + 100, or 1000 projecitons. The number of samples of attenuation profiles in the raw data equals thenumber of detectors time the number of projections 715 detectors x 1000 projections samples

  37. 22. A smooth, or low-pass, reconstruction filter is typically NOT selected for a(n) _____ exam.

    D. Internal auditory canals
  38. 12. In a _____, the highest pixel values from a stack of CTA images are projected along many "rays"

    C. MIP
  39. 3. The x-ray beam used in CT scanning is _____ the patient's tissues.
    1. reflected off of
    2. attenuated by
    3. generated by

    B. 2 only
  40. How many samples of information comprising the raw data are there for a third generation, 64 row detector scanner with 850 detectors and 1700 projections acquired during a 360 degree rotation?

    • C. 92,480,000
    • 850 x 1700 x 64 = 92,480,000
  41. Reconstruction filter, or Kernel, is a filter that is applied to the raw date during image reconstruction. What is the process of applying this filter called?

    C. convolution
  42. What are the two basic types of reconstruction filters?
    Smooth and Sharp
  43. Which post-processing techniques use the image date?
    1. multi-planar reconstruction
    2. retrospective reconstruction
    3. 3D shaded surface display

    • C. 1 and 3 only
    • retrospective reconstruction uses raw image data
  44. The most accurate MIP results are obtained when a _____ volume of interest is selected.
    a. large
    b. small
    b. small
  45. Cone beam reconstruction is used when there are more than ____ slices in a single rotation being acquired.

    • B. 4
    • Filtered Back Projection is used when less than 4
  46. 9. Iterative reconstruction is:

    A. a complex cycle of correction calculations applied during image reconstruction in order to reduce noise in the image
  47. 14. Important clinical benefits of iterative reconstruction include:
    1. ability to reduce radiation dose without compromising image quality
    2. no longer needing to perform multi-planar reconstructions
    3. reduction in noise seen in the image

    C. 1 & 3
Card Set
MIC Ch2 CT Image Formation
CT Image Formation