CT Imaging review

  1. what is interpolation?
    a mathematical method of estimating an unknown value using the know values on either side of the unknown
  2. increasing the scan field of veiw __________
    increases the number of detector cellls collecting data
  3. what is the function of the digital-to-analong converters?
    converts the signal from the computer into an analog signal for the display monitor
  4. what hounsfield values are in the naturally occurring range (i.e., not manmade objects like surgical clips)?
    -1000 to 1000
  5. decreasing the window width in an image decreases ____
    the anatomic diversity displayed
  6. the window width of a ct image is set at 300,  and the leve (or center) is set at 100. how is a structure with a measurement of 280 HU displayed?
  7. what is included in the scan parameters?
    • mA
    • scan time
    • slice thickness
    • FOV
    • scan algorithm
    • kVp
    • pitch
  8. what is the uncoupling effect?
    even when mA or kVp setting that is too high is used a good image results, making it difficult to determine when a dose is higher than necessary.
  9. what is a disadvantage of a bone algorithm?
    it reduces the visibibility of soft tissue structures
  10. what is a partial scan?
    a scan that collects data from 180 degree tube arc, plus the degree of arc of the fan angle
  11. what is the true test of the quality of a specific image?
    spatial resolution and contrast resolution
  12. how often is the accuracy of a scanner's slice thickness tested?
  13. what can be done to improve the linearity of a ct system?
    daily calibrations
  14. what quality control test must be preformed by a medical physicist?
    radiation dose measurements
  15. artifacts that reult from undersampling are called ___
    aliasing artifacts
  16. raw data that results from an MDCT scan is used so that the 1-mm slices are combined to produce thicher slices for viewing. this is called ___
    image reconstruction
  17. True or False
    MPRs can be created either at the operator's console or at a separate workstation
  18. what is a limitation of scanner-created MPRs?
    in most cases, only straight sagittal and coronal planes can be automatically generated
  19. in creating a surface rendered image, what can happen if the threshold set is too narrow?
    actual protruding structures can be imperceptible
  20. True or False
    a MIP is a good method to display contrast filled arteries
  21. True or False
    a MIP is a good method to display the bronchial tree
  22. what has become the favored 3D imaging technique in CT?
    volume rendering
  23. what type of reconstruction is used in a 1st generation CT Scanner?
  24. what is the largest deterrent of a scanner's contrast resolution?
  25. how do you determine the minimum oject size that a scanner can resolve?
    taking the reciprocal value of the scanner's limiting resolution.

    explanation: a line pair is a line and the space so this value can be divided in half
  26. any ___ in the voxel dimension increases nois, or decreases the signal to noise ratio.
  27. what is used for current MDCT image reconstruction?
    180 interpoltion
  28. how many HU can there be for any given pixel?
  29. how do you calculate the display field of view?
    pixel dimension multiplied by the matrix size
  30. HU with less attenuation than water are ___
  31. HU with more attenuation than water are ___
  32. pixels that differ by 1 HU represnt a ___ difference in attenuation.
  33. explain a hybrid array.
    detector array that contains mid line narrow elements flanked by wider detectors
  34. what does the spatial resolution of a scanner control?
    its ability to image small structures
Card Set
CT Imaging review
image reconstruction, image display, image quality, QA, post processing