ARRT ARRT CT Artifacts and Troubleshooting 1 — Questions and Answers
Question 1: What type of artifact appears as bright or dark streaks radiating from high-density objects like metal implants in CT images?
- Beam hardening artifact (Correct answer)
- Ring artifact
- Motion artifact
- Partial volume artifact
Correct answer: Beam hardening artifact
Beam hardening artifacts appear as streaks or dark bands radiating from dense metallic objects because lower-energy photons are preferentially absorbed.
Question 2: A ring or band artifact centered on the image is most likely caused by a malfunction of which CT component?
- X-ray tube
- A single detector element (Correct answer)
- Collimator
- Gantry motor
Correct answer: A single detector element
Ring artifacts result from a miscalibrated or malfunctioning detector element producing a circular artifact at a fixed radius from the isocenter.
Question 3: Which artifact is caused by patient movement during CT data acquisition and appears as blurring or ghosting on the reconstructed image?
- Partial volume artifact
- Motion artifact (Correct answer)
- Aliasing artifact
- Cupping artifact
Correct answer: Motion artifact
Motion artifacts result from patient movement during scanning, causing inconsistent data at each projection angle and manifesting as blurring or streaking.
Question 4: The 'cupping artifact' in CT, where the center of a uniform object appears less dense than its periphery, is a manifestation of which phenomenon?
- Aliasing
- Beam hardening (Correct answer)
- Quantum noise
- Partial volume averaging
Correct answer: Beam hardening
Cupping artifact is a form of beam hardening where the edges of the object appear brighter because the beam hardens less traveling a shorter path length.
Question 5: Partial volume averaging artifacts in CT are best reduced by which acquisition parameter adjustment?
- Increasing mAs
- Using a thinner slice thickness (Correct answer)
- Increasing kVp
- Widening the display window
Correct answer: Using a thinner slice thickness
Thinner slices reduce partial volume averaging by ensuring each voxel contains tissue from a smaller volume, improving accuracy of CT numbers.
Question 6: Aliasing artifacts in CT, which appear as fine streaks or Moiré patterns, are caused by which factor?
- Insufficient detector sampling (Correct answer)
- High kVp settings
- Excessive patient size
- Incorrect table speed
Correct answer: Insufficient detector sampling
Aliasing artifacts occur when the object being imaged contains spatial frequencies higher than the detector sampling rate can capture, per the Nyquist theorem.
ARRT ARRT CT Artifacts and Troubleshooting 1
What type of artifact appears as bright or dark streaks radiating from high-density objects like metal implants in CT images?