Computed Tomography Test Computed Tomography Ultimate 3 — Questions and Answers
Question 1: A patient has a serum creatinine of 2.8 mg/dL. What is the most appropriate action before administering iodinated contrast?
- Proceed normally
- Administer double the usual contrast volume
- Consult with the ordering physician and consider pre-hydration or alternative imaging (Correct answer)
- Cancel the study entirely without consultation
Correct answer: Consult with the ordering physician and consider pre-hydration or alternative imaging
Elevated creatinine indicates impaired renal function; the clinical team should assess the risk-benefit ratio and consider IV hydration or alternative modalities.
Question 2: Which CT technique uses two X-ray tubes operating at different kilovoltage peaks simultaneously?
- Cone-beam CT
- Dual-energy CT (Correct answer)
- Helical CT
- Sequential CT
Correct answer: Dual-energy CT
Dual-energy CT employs two X-ray sources at different kVp settings (e.g., 80 and 140 kVp) to exploit differences in tissue attenuation based on photon energy.
Question 3: What is the role of the 'anti-scatter grid' in CT imaging?
- It collimates the primary beam before it reaches the patient
- It reduces scattered radiation reaching the detectors (Correct answer)
- It filters out low-energy photons from the X-ray beam
- It measures patient dose in real time
Correct answer: It reduces scattered radiation reaching the detectors
Anti-scatter grids are placed in front of detectors to absorb scattered photons that would otherwise degrade image contrast and quality.
Question 4: Which contrast injection phase best visualizes hepatocellular carcinoma (HCC)?
- Non-contrast
- Arterial phase (Correct answer)
- Portal venous phase
- Delayed phase
Correct answer: Arterial phase
HCC is hypervascular and enhances avidly during the arterial phase (approximately 25-35 seconds after injection) when hepatic artery flow predominates.
Question 5: What does ALARA stand for in radiation protection?
- As Low As Reasonably Achievable (Correct answer)
- Automatic Level Adjustment for Radiation Areas
- Allowable Limit for Any Radiation Application
- Adjusted Limit of Acceptable Radiation Activity
Correct answer: As Low As Reasonably Achievable
ALARA is the guiding principle in radiation protection meaning doses should be kept as low as reasonably achievable while maintaining diagnostic image quality.
Question 6: Which parameter directly determines the thickness of a CT slice in single-detector row scanners?
- Detector aperture width (Correct answer)
- X-ray tube current
- Pitch factor
- Reconstruction kernel
Correct answer: Detector aperture width
In single-detector scanners, slice thickness is controlled by pre-patient and post-patient collimation, which determines the detector aperture width.
Question 7: A ring artifact on a CT image is most likely caused by:
- Patient motion during scanning
- A faulty detector element (Correct answer)
- Metallic implants in the patient
- Incorrect window level settings
Correct answer: A faulty detector element
Ring artifacts are caused by a malfunctioning or uncalibrated individual detector element that consistently records incorrect attenuation values.
Computed Tomography Test Computed Tomography Ultimate 3
A patient has a serum creatinine of 2.8 mg/dL.
What is the most appropriate action before administering iodinated contrast?