Computed Tomography Test Computed Tomography Knowledge Questions and An 5 — Questions and Answers
Question 1: Which CT finding is most characteristic of acute appendicitis?
- Appendix diameter <5 mm with periappendiceal fat stranding
- Appendix diameter >6 mm with periappendiceal fat stranding and wall enhancement (Correct answer)
- Appendiceal calcification without surrounding inflammation
- Free air beneath the diaphragm
Correct answer: Appendix diameter >6 mm with periappendiceal fat stranding and wall enhancement
Acute appendicitis classically appears as an inflamed, dilated appendix (>6 mm) with periappendiceal fat stranding and wall hyperenhancement on CT.
Question 2: What is the purpose of using a higher kVp setting when scanning a bariatric patient?
- To reduce scan time
- To increase penetrating power of the X-ray beam through greater tissue thickness (Correct answer)
- To decrease patient radiation dose
- To improve temporal resolution for cardiac imaging
Correct answer: To increase penetrating power of the X-ray beam through greater tissue thickness
Higher kVp produces more energetic photons with greater penetrating ability, reducing photon starvation and noise when imaging larger patients with greater tissue attenuation.
Question 3: On a CT abdomen, a lesion measures -120 HU. What does this attenuation value suggest?
- Calcified granuloma
- Simple cyst
- Fat-containing lesion (lipoma or angiomyolipoma) (Correct answer)
- Acute hemorrhage
Correct answer: Fat-containing lesion (lipoma or angiomyolipoma)
Fat has a characteristic negative attenuation of approximately -50 to -150 HU, so a value of -120 HU strongly indicates a fat-containing lesion.
Question 4: What is the function of the CT gantry?
- Houses the patient table and controls its movement
- Contains the rotating X-ray tube and detector array that surrounds the patient (Correct answer)
- Processes and reconstructs raw CT data into images
- Injects and controls IV contrast delivery
Correct answer: Contains the rotating X-ray tube and detector array that surrounds the patient
The gantry is the large ring-shaped housing that contains the X-ray tube and detector array, which rotate around the patient during data acquisition.
Question 5: Which condition is best diagnosed using CT pulmonary angiography (CTPA)?
- Community-acquired pneumonia
- Pulmonary embolism (Correct answer)
- Pulmonary fibrosis
- Pleural effusion
Correct answer: Pulmonary embolism
CTPA is the gold standard for diagnosing pulmonary embolism, demonstrating filling defects within pulmonary arteries during the pulmonary arterial phase.
Question 6: What does 'window leveling' (adjusting the level/center) primarily affect in a CT image?
- The overall brightness or density of the displayed image (Correct answer)
- The range of HU values displayed (contrast)
- The spatial resolution of the image
- The radiation dose delivered to the patient
Correct answer: The overall brightness or density of the displayed image
The window level (center) sets the midpoint of the displayed HU range, shifting the image brighter or darker without changing the range of visible values.
Question 7: In CT, what is the significance of a 'negative predictive value' of 99% for ruling out pulmonary embolism with CTPA?
- 99% of patients with PE will have a positive CTPA
- If CTPA is negative, there is a 99% chance the patient truly does not have PE (Correct answer)
- CTPA correctly identifies 99% of all pulmonary vessels
- 99% of CTPA studies are technically adequate for interpretation
Correct answer: If CTPA is negative, there is a 99% chance the patient truly does not have PE
A 99% negative predictive value means that a negative CTPA result is highly reliable for excluding PE, with only a 1% chance of a false-negative result.
Computed Tomography Test Computed Tomography Knowledge Questions and An 5
Which CT finding is most characteristic of acute appendicitis?