Computed Tomography Knowledge Questions and An Flashcards
7 cards from real Computed Tomography Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Computed Tomography Knowledge Questions and An flashcards as text
Which parameter directly controls the amount of radiation delivered per CT rotation?
Answer: mAs
Milliampere-seconds (mAs) is the product of tube current and rotation time, directly determining the number of X-ray photons produced per rotation.
A patient's CT scan demonstrates a hyperdense lesion in the basal ganglia on non-contrast CT. What is the most common cause?
Answer: Acute hemorrhage
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.
What is the primary purpose of automatic exposure control (AEC) in CT?
Answer: Modulate tube current to maintain consistent image quality while minimizing dose
AEC (also called tube current modulation) adjusts mA in real time based on patient attenuation, maintaining target noise levels while reducing unnecessary radiation.
Which CT artifact appears as a star-burst pattern of dark and light streaks emanating from a dense object?
Answer: Metallic streak artifact
Metallic streak artifacts are caused by extreme beam hardening and photon starvation from highly attenuating metal implants, producing characteristic streak patterns.
What is the purpose of the 'scout' or 'topogram' image acquired before a CT scan?
Answer: To plan scan range, angulation, and protocol parameters
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.
In multidetector CT (MDCT), what does the term 'detector configuration' refer to?
Answer: The number of active detector rows and their width used during acquisition
Detector configuration describes how many detector rows are activated and the width of each row, determining the acquired slice thickness per rotation.
Which intravenous contrast phase best demonstrates hepatocellular carcinoma (HCC)?
Answer: Hepatic arterial phase (25–35 seconds)
HCC is hypervascular and receives arterial supply, causing peak enhancement during the hepatic arterial phase before the rest of the liver enhances via portal flow.