Computed Tomography Test Computed Tomography (CT) 4

Question 1

What is the recommended contrast injection rate for a CT pulmonary angiography (CTPA) exam?

Accepted Answer

3–5 mL/s

Answer

CTPA typically requires a brisk injection rate of 3–5 mL/s to achieve adequate opacification of the pulmonary arteries within the narrow bolus window.

Question 2

Which CT scan parameter, when increased, reduces partial volume averaging artifact?

Accepted Answer

Decreasing slice thickness

Answer

Thinner slices reduce the volume of tissue averaged within each voxel, minimizing partial volume artifact and improving detection of small lesions.

Question 3

A ring artifact in CT is most commonly caused by:

Accepted Answer

Malfunction of one or more detector elements

Answer

Ring artifacts result from a miscalibrated or malfunctioning detector element that consistently misreads attenuation values, creating a characteristic ring or arc pattern.

Question 4

In CT colonography (virtual colonoscopy), what is the standard patient preparation requirement?

Accepted Answer

Bowel cleansing and colonic insufflation with CO₂ or air

Answer

CT colonography requires bowel prep to clear stool and distension of the colon with gas to allow detection of polyps and mucosal lesions.

Question 5

What is the formula for CT number (Hounsfield unit)?

Accepted Answer

HU = (μ_tissue − μ_water) / μ_water × 1000

Answer

The Hounsfield unit is calculated as the difference between tissue and water attenuation divided by water attenuation, multiplied by 1000, placing water at 0 HU.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test Computed Tomography (CT) 4