Study Guide 2

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radiated1
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8356
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Study Guide 2
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2010-03-07 10:33:39
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CT Image Formation
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CT Image Formation
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  1. Using _____ reconstruction filter would decrease the apparence of noise in a CT image.
    1. no
    2. a sharp
    3. a smooth
    a. 1 only
    b. 2 only
    c. 2 and 3
    d. 3 only
    d
  2. A _____ scan uses only a single projection.
    1. conventional, or serial
    2. hilical
    3. localizer
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    c
  3. Which of the following statements is FALSE regarding 3D SSD?
    a. helical image data is well suited for 3D SSD because there is minimal misregistration or gaps
    b. the volume data, from which the 3D SSD is generated, is created by combining transverse, sagittal, and coronal reconstructions
    c. the tissue surface may be selected by using a threshold value equal to the tissue's CT number
    d. patient motion during the scan is detrimental to the quality of the 3D images
    b
  4. Which type(s) of storage media may hold CT image data?
    1. internal hard disk
    2. CD
    3. re-writable optical disk
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    d
  5. _____ may have to be edited fom the data set to get a diagnostic MIP of a CTA exam.
    a. Iodinated contrast media
    b. Vessells of interest
    c. Air
    D. Bones
    d
  6. Which of the following is NOT an advantage of a helical study compaired to a conventional, serial CT study?
    a. minimal anatomical misregistration sometimes caused by inconsistent breath-holding
    b. shorter total exam time
    c. can retrospectively reconstruct a slice at any arbitrary position
    d. offers the best imge quality for a brain exam
    d
  7. Which of the following utilizes convolution?
    1. 3D SSD
    2. Fourier transform
    3. filtered back projection
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    c
  8. 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?
    a. volume rendering
    b. multi-planar reconstruction
    c. maximum intensity projection
    d. 3D shaded surface display
    d
  9. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    a
  10. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    c
  11. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    b
  12. A retrospective reconstruction, in which the reconstruction field-of-view is varied, uses:
    a. a reconstructed image in the sagittal plane
    b. CT raw data
    c. more photons
    d. CT image data
    b
  13. Which of the following is common to both a localizer scan and a conventional, serial CT scan?
    a. they both produce digital images
    b. the patient table moves at a constant velocity
    c. they both produce cross-sectional images
    d. the x-ray tube make complete 360* rotations
    a
  14. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    d
  15. _____ is the mathematical process used by single-row detector scanners to reconstruct CT images from raw data.
    a. Weighted averaging
    b. Filtered back projection
    c. The Fourier transform
    d. Integration of the area under the curve
    b
  16. 3D shaded surface displays are performed on CT:
    1. image data
    2. raw data
    3. attenuation profiles
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    a
  17. A pixel is a:
    a. bright artifact on a film
    b. single 3D volume element within a volume of anatomical data
    c. singe 2D picture element within the image plane
    d. range of gray levels on a CT image
    c
  18. The pencil thin section of the x-ray fan beam that strikes a single detector is called a:
    a. line
    b. projection
    c. view
    d. ray
    d
  19. A kernel is a:
    a. component in the x-ray tube
    b. post-processing filter applied to image data
    c. type of detector
    d. filer applied to the CT rawdata
    d
  20. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    a
  21. CTA images come from a _____ scan
    1. conventional, or serial
    2. helical
    3. localizer
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    b
  22. If an image matrix has 360 rows and 360 columns, how manyu pixels are there in the image?
    a. 21,600
    b. 129,600
    c. 259,200
    d. 379,800
    b-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. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    b
  24. Which of the following is a reconstuction technique applied to the raw data after the primary reconstruction has already been accomplished?
    a. maximum intensity projection
    b. volume rendering
    c. retrospective reconstruction
    d. multi-planar reconstruction
    c
  25. What does convolution do to the image quality when it si added to the back projection reconstruction process?
    a. normalizes the attenuation coefficients to ensure tissues are displayed with correct CT numbers
    b. increases the nubmer of projections thereby reducing streaking artifacts
    c. improves contrast resolution by reducing scatter radiation
    d. enhances important characteristics of attenuation profiles thus reducing streak and star artifacts
    d
  26. 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 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    d
  27. _____ allows helical data to be converted into planar raw data.
    a. Retrospective reconstruction
    b. Interpolation
    c. Cone beam reconstruction
    d. Convolution
    b
  28. What is the most common type of film used for recording CT images?
    a. thermal
    b. double emulsion
    c. single emulsion
    d. paper
    c
  29. A helical scan performed on a 64 slice MDCT scanner is reconstruction with:
    a. back projection
    b. simple reconstruction because it is a single projection scan
    c. no reconstruction filter
    d. cone beam reconstruction
    d
  30. _____ yields an image that appears 3D but also shoes anatomical details above and below the 3D surface.
    a. SSD
    b. VR
    c. MIP
    d. Multi-planar reconstruction
    b
  31. MDCT scanners capable of collecting 64 slices in a single rotation do NOT:
    a. perform conventional CT scans
    b. perform helical CT scans
    c. use filered back projection as their method of image reconstruction
    d. perform localizer scans
    c
  32. MIP images:
    a. are most frequently used for visualixing air-filled spaces
    b. can NOT be run in a cine loop
    c. are most accurate when a large volume of interest is selected
    d. do NOT demonstrate detail beneath the brightest pixel
    d
  33. Multi-planar reconstructions are performed on which of the following?
    1. image data
    2. raw data
    3. attenuation profiles
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    a
  34. The _____ move(s) during a helical scan on a third-generation scanner,.
    1. x-ray tube
    2. patient table
    3. detector elements
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    d
  35. 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
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1, 2 and 3
    a
  36. 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?
    a. 286,000
    b. 648,500
    c. 715,000
    d. 845,000
    c--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. A smooth, or low-pass, reconstruction filter is typically NOT selected for a(n) _____ exam.
    a. pituitary
    b. kidneys
    c. liver
    d. internal auditory canals
    d
  38. In a _____, the highest pixel values from a stack of CTA images are projected along many "rays"
    a. SSD
    b. MIP
    c. PR
    d. VR
    b
  39. The x-ray beam used in CT scanning is _____ the patient's tissues.
    1. reflected off of
    2. attenuated by
    3. generated by
    a. 1 only
    b. 2 only
    c. 3 only
    d. 1,2 and 3
    b

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