Computed Tomography Test Computed Tomography Knowledge Questions and An 3

Question 1

Which parameter directly controls the amount of radiation delivered per CT rotation?

Accepted Answer

mAs

Answer

Milliampere-seconds (mAs) is the product of tube current and rotation time, directly determining the number of X-ray photons produced per rotation.

Question 2

A patient's CT scan demonstrates a hyperdense lesion in the basal ganglia on non-contrast CT. What is the most common cause?

Accepted Answer

Acute hemorrhage

Answer

Fresh blood is hyperdense on non-contrast CT (55–80 HU) due to the protein content of clotted hemoglobin, making acute hemorrhage the most common cause of basal ganglia hyperdensity.

Question 3

What is the primary purpose of automatic exposure control (AEC) in CT?

Accepted Answer

Modulate tube current to maintain consistent image quality while minimizing dose

Answer

AEC (also called tube current modulation) adjusts mA in real time based on patient attenuation, maintaining target noise levels while reducing unnecessary radiation.

Question 4

Which CT artifact appears as a star-burst pattern of dark and light streaks emanating from a dense object?

Accepted Answer

Metallic streak artifact

Answer

Metallic streak artifacts are caused by extreme beam hardening and photon starvation from highly attenuating metal implants, producing characteristic streak patterns.

Question 5

What is the purpose of the 'scout' or 'topogram' image acquired before a CT scan?

Accepted Answer

To plan scan range, angulation, and protocol parameters

Answer

The scout (localizer) image is a low-dose 2D projection used to define the scan range, check patient positioning, and confirm the correct anatomical area.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test Computed Tomography Knowledge Questions and An 3