CT REVIEW

  1. Which of the following is not considered part of the middle mediastinum



    B. Thoracic Aorta
  2. The trigger threshold for the Pulmonar Embolus CT exam is _____ HU.




    D . 0 - 50
    B. 90-100
  3. Which of the following processes is associated with reconstructing volumetric acquired data to make the data look like individual slices?



    B. linear interpolation
  4. Backprojection is associated with:




    A. Artifacts
  5. Which of the following techniques is used to reduce metal artifacts....Orthopedic Appliance?




    C. Increased KvP/Increased MaS/ Increased Pitch
  6. Which of the following might be administered in a CT Urography to increase urinary output?



    A. Furosmide
  7. The DAS is located:




    C. Between the detectors and the Computer
  8. Filament size is directly related to

    1 slice thickness
    2 mA selected
    3 spatial resolution




    C. 1+2+3

    All of the above
  9. The diaphragm's movement depends of which of the following nerves?




    A. Phrenic
  10. The Renal Arteries correspond to the level of:




    A. L2
  11. Backprojection is associated with:




    B. Artifacts
  12. Which 3 veins empty into the portal Vein?




    B. Splenic, IMA,SMA
  13. When image date is acquired by a CT scanner, it goes through a process known as:




    A. Quantization
  14. What happens when you increase the Display field of view?
    • *More photons interact with the pixels.
    • * Noise decreases
    • *Spatial Resolution Decreases
    • *Larger pixels
  15. What happens when you decrease the display field of view?
    • *Smaller pixels
    • *Spatial Resolution increases.
    • *Noise increses
    • * Displays a larger area on the screen.
  16. How to improve Contrast Resolution?
    • *Higer mA
    • *Smaller Pt
    • *Larger DFOV
    • *Larger pixels
    • *Smaller Matrix
    • *Increase Collimation
    • *Smooth Filter

    Contrast resolution is improved when more photons reach the detectors. More noise decreases Contrast resolution. Technical factors that decrease noise increase contrast resolution.
  17. How to Improve Spatial resolution?
    • *Smaller detector size
    • *Smaller DFOV
    • *Smaller pixels
    • *Thinner slices
    • *Small focal spot
    • *narrow collimation
    • Ability of a scanner to display fine detail, sometimes referred to high contrast spatial resolution.
  18. What improves noise?
    • *Higher mAs
    • *Larger Pixels
    • *Larger Slice thickness
    • *Larger Display field of View


    *When ever more photons interact with the detectors, decrease the noise inherent in the image.
  19. Image linearity is defined as?




    B. The relative accuracy between calculated CT # and their respective linear attenuation coefficient.
  20. Spatial Resolution is best defines.




    C. Ability to image very small objects.

    • *Small pixel size, small detector size, thin slices, small focal spot, and narrower collimation improve image detail.
    • *When you do anything that increases the noise levels in the image, you also improve the Spatial Resolution.
  21. Contrast resolution is improved by:




    • C. Increasing mAs
    • *Thicker slices, imaging smaller pt, using low noise imagers, larger Fov, smaller matrix size, smooth reconstruction filters. Scatter radiation reduces contrast resolution

    * Anything that reduces noise increases Contrast resolution.
  22. Contrast resolution of a CT scanner is not related to which of the following:



    A. Focal spot size.

    *Want everything large to reduce the inherent noise level. Focal spot size is the only thing that doesnt affect noise.
  23. Spatial resolution is improved by:
    A. Small detector size.
    B. Small pixel size.
    C. Small voxel size.
    D. Small patient.
    ABC

    *small detector size, small pixel size, small voxel size, small focal spot size, High freq filter, and narrow pre detector collimator. Anything that gives you higher image noise improves spatial resolution.
  24. Which of the following improve contrast resolution?




    • D.
    • C.

    Anything that reduced image noise improves contrast resolution. Larger FoV increases the size of the pixels thus reducing image noise, improving contrast resolution.
  25. The term_____describes the ability of a CT Scanner to differentiate objects with minimal differences in attenuation coefficients?



    C. Contrast resolution.
  26. Which of the following is reduced by the use of high KvP during CT?



    • C. Photoelectric Absorption
    • C. Xray tube loading.

    Bean hardening is also reduced.
  27. Abdominal Aorta bifurcates at the level of :



    D. L4: where if bifurcates into the left and right common iliac artery. Caude Equina is also located at the level of L4

    The spinal coard ends at L2.
  28. After the injection of IV contrast for a CT of the brain; what area does not enhance?



    D. Posterior Horns of the Lateral Ventricle

    *this area contains cerebral spinal fluid and doesnt enhance.
  29. Ct scanning of the liver for tumor evaluation should not be performed during which phase of contrast enhancement?



    C. Equlibrium; its the lowest point of enhancement

    *the order is as follows: Bolus, Non equilibrium, Equilibrium.
  30. The hepatic Arterial phase occurs about ____ seconds after the start of the IV injection?



    D. 20-40 seconds after injection.
  31. The portal venous phase occurs at about ___seconds after the start of injection.



    D. 60-90

    *Hepatic early arterial 20-40 seconds; Portal venous @ 60-90secs
  32. Which of the following would not enhance during the first several minutes of a post contrast CT study of the neck?




    C. Lymph Nodes
  33. Which of the following is Considered to be Iso Osmolar contrast media?



    C. Iodixanol

    The rest are all Non Ionic Low Osmolar Contrast media
  34. Non Ionic Low Osmolar Contrast Media
    Iohexol Omnipaque
    Iopamidol Isovue
    Ioversol Optiray
  35. Ionic High Osmolar Contrast Media
    Iothalmate Conray
    Diatrizoate Hypaque
  36. Radiation exposure and its potential harmful effects have a relationship that is termed_____in nature.



    D. Stochastic

    Certain hermfull effects of exposrue to diagnostic xrays, such as cancer formation and genetic mutations are said to be random or Stochastic in nature

    Stochastic effects is one that has no threshold dose but increases in probability with increases dose.
  37. Radiation dose index calculation that takes into account the variations in absorbption across the field of view due to beam hardening is termed




    B. CTDI w

    is calculated from measurements made with dosimeter positioned at the center and periphery of a phantom and accounts for the veriences in dose distribution due to the effect of beam hardening.
  38. Amount of xray energy absorbed in a unit of mass is measured in ?

    What is it?
    Gray Gy

    Its is the Absorbe dose.
  39. Type of tissue radiotion is deposited in?

    Measured in?
    or
    Quantity of Absorbed radiation dose based on the radiosensitivity of a particular tissue is called?
    It is the Effective dose

    Measured in Seiverts
  40. Approximate mesure of the dose received in a single section or slice?
    CTDI
  41. Average cumilative dose to each slice within the center of a scan, consisting of multiple slices; including scatter radiation.
    MSAD
  42. Moderate reaction to contast media
    • *mild bronchospasm
    • *moderate to severe urticaria
    • *vasovagal response
    • *tachycardia from hypotension
  43. Severe reaction to contrast media
    • Profound hypotension
    • Laryngeal edema
    • Pulmonary edema
    • Severe bronchospasm
    • Chronic arrythmia
    • Seizures
    • Cardiopulmonary arrest
    • Death
  44. Normal unenhanced liver density measures?
    unenhanced density of 45-65
  45. Peak arterial phase for the liver?
    • Peak arterial enhancement of the liver is 25-35 secs after injection.
    • *hepatic arterial supply well opacified
    • *no parenchymal enhancement
    • -for early arterial is 15-20
  46. When does the Portal Hepatic venous Phase occur?
    • -60-70 seconds after injection.
    • -peak hepatic parenchyma enhancement.
    • -contrast redistributes from blood into extravascular spaces.
    • -demonstrates hypervascular lesions such as hepatic mets.
  47. When does the liver equilibrium phase occur?
    • - 2-3 minutes after injection
    • -hepatic parenchymal enhancement dissipitates
    • -minimal difference in contrast between intra/extavascular spaces
    • - many lesions become indistinguishable between surrounding tissue.
  48. When does the liver delayed phase occur?
    • 5-20 minutes after injection
    • -demonstrates the complete fill in of a hemangioma as it becomes isodense with the surrounding parenchyma
  49. When does the corticomedullary phase occur?
    • - late arterial phase 30-40 seconds
    • -optimal enhancement of the renal cortex/vein
    • -medulla minimally enhanced; allowing maximum differentiation from renal cortex.
  50. When does the nephrographic phase occur?
    • -70-90 secs after injection
    • -enhancement differences between renal cortex and medulla reach equillibrium
    • -optimal for lesions.
  51. When does the excretory phase occur?
    • -delayed imaging phase; 3 minutes after injection
    • -contrast agent becomes excreted into the renal calyces;opacifying the renal pelvis, ureters and bladder.
    • -visualized filling defects.
  52. When does the arterial phase of the Kidneys occur?
    * 20-25 secs delay; maximum opacification of the aorta/renal arteries.
  53. What is effective mAs?
    What is the formula for the effective mAs?
    • its is the calculated mas per aquired slice;
    • -primary factor is table speed

    -mas/pitch
Author
eastrhodeislandkilla
ID
153382
Card Set
CT REVIEW
Description
ERT'S Review Q's
Updated