2016 AAPM Annual Meeting
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Session Title: CT Systems Course
Question 1: Low Contrast Detectability (LCD) for a helical CT scan is affected by the following data acquisition and reconstruction parameters except for?
Reference:J. Hsieh, Computed Tomography: principles, design, artifacts, and recent advances, 3rd ed., SPIE press, 2015.
Choice A:mAs (tube current x gantry rotation period).
Choice B:kVp.
Choice C:Image slice thickness.
Choice D:Image reconstruction interval.
Choice E:Reconstruction kernel.
Question 2: In CT, the radiation dose to individual patient is better described by “organ dose”. Which of the following CT dose metrics is the best approximation to the dose received by liver from a routine abdominal CT?
Reference:Moore BM, Brady SL, et al. “Size-specific dose estimate (SSDE) provides a simple method to calculate organ dose for pediatric CT examinations”, Medical Physics: 41(7), July, 2014
Choice A:CTDIvol.
Choice B:Size Specific Dose Estimate (SSDE).
Choice C:Dose Length Product (DLP.
Choice D:Effective Dose.
Choice E:None of the above.
Question 3: For CT low dose lung cancer screening, ACR recommends a set of requirements for a designated lung cancer screening site. Which of the following is NOT one of the ACR requirements?
Reference:ACR–STR PRACTICE PARAMETER FOR THE PERFORMANCE AND REPORTING OF LUNG CANCER SCREENING THORACIC COMPUTED TOMOGRAPHY (CT). http://www.acr.org/~/media/ACR/Documents/PGTS/guidelines/LungScreening.pdf
Choice A:Single Breathhold.
Choice B:Dose Length Product (DLP) ≤ 100mGy*cm.
Choice C:Image thickness 2.5mm.
Choice D:Gantry rotation period ≤ 0.5s.
Choice E:Number of physical detector rows 16.
Question 4: A set of parallel projections was acquired with a CT gantry that rotates clockwise over 2?. A student developed a parallel-beam reconstruction algorithm and made one mistake by assuming the gantry rotates counterclockwise. What is the relationship, if any, between the image reconstructed by the student and the correctly reconstructed image?
Reference:J. Hsieh, Computed Tomography: principles, design, artifacts, and recent advances, 3rd ed., SPIE press, 2015.
Choice A:It is rotated 180-degree.
Choice B:It is flipped.
Choice C:There is no relationship between the two images.
Question 5: An image was original reconstructed to 50cm FOV and then zoomed to 25cm FOV with image-space interpolation to produce the final image, f. Another image, f’, was generated with a targeted reconstruction to 25cm FOV (all other parameters were kept the same). Which of the following statement is true?
Reference:J. Hsieh, Computed Tomography: principles, design, artifacts, and recent advances, 3rd ed., SPIE press, 2015
Choice A:f’ has a positive CT number shift compared to f
Choice B:f’ is sharper than f
Choice C:f’ is less noisy than f
Question 6: Beam-hardening artifact is caused by:
Reference:H. E. Johns and J. R. Cunningham, The Physics of Radiology, Charles C. Thomas Publisher Ltd., Springfield, IL (1983).
Choice A:Polychromatic x-ray spectrum from the x-ray tube.
Choice B:Energy-dependent nature of attenuation coefficient.
Choice C:Patient motion during data acquisition.
Choice D:A and B.
Choice E:A, B, and C.
Question 7: Possible causes of CT image artifacts are:
Reference:J. Hsieh, Computed Tomography: principles, design, artifacts, and recent advances, 3rd ed., SPIE press, 2015.
Choice A:Nature of x-ray physics.
Choice B:Limitations of CT Technology.
Choice C:Patient-induced effects.
Choice D:All of the above.
Question 8: The CT detector scintillator converts X-rays into?
Reference:J. Hsieh, “Computed Tomography: Principles, designs, artifacts, and recent advances”, SPIE Press, Bellingham, WA.
Choice A:Light
Choice B:Electrons
Choice C:Photons
Choice D:Current
Choice E:Gas
Question 9: The most likely artifact produced by a third-generation CT detector is a?
Reference:J. Bushberg, J. Seibert, E. Leidholdt, J. Boone, “The essential physics of medical imaging”, Lippincott Williams & Wilkins.
Choice A:Doubloon
Choice B:Ring
Choice C:Vase
Choice D:Statue
Choice E:Shard
Question 10: Assuming the filament length is constant, which one of the following statements regarding the anode angle of X-ray tube in CT is true?
Reference:J. Bushberg, J. Seibert, E. Leidholdt, J. Boone, “The essential physics of medical imaging”, Lippincott Williams & Wilkins.
Choice A:Smaller anode angle provides better spatial resolution, larger field coverage, less heel effect, and higher power loading.
Choice B:Smaller anode angle provides worse spatial resolution, smaller field coverage, stronger heel effect, and less power loading.
Choice C:Larger anode angle provides better spatial resolution, larger field coverage, stronger heel effect, and higher power loading.
Choice D:Larger anode angle provides worse spatial resolution, larger field coverage, less heel effect, and lower power loading.
Choice E:None of above is correct.
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