Computed Tomography (CT) 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 (CT) flashcards as text
What is the recommended contrast injection rate for a CT pulmonary angiography (CTPA) exam?
Answer: 3–5 mL/s
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.
Which CT scan parameter, when increased, reduces partial volume averaging artifact?
Answer: Decreasing slice thickness
Thinner slices reduce the volume of tissue averaged within each voxel, minimizing partial volume artifact and improving detection of small lesions.
A ring artifact in CT is most commonly caused by:
Answer: Malfunction of one or more detector elements
Ring artifacts result from a miscalibrated or malfunctioning detector element that consistently misreads attenuation values, creating a characteristic ring or arc pattern.
In CT colonography (virtual colonoscopy), what is the standard patient preparation requirement?
Answer: Bowel cleansing and colonic insufflation with CO₂ or air
CT colonography requires bowel prep to clear stool and distension of the colon with gas to allow detection of polyps and mucosal lesions.
What is the formula for CT number (Hounsfield unit)?
Answer: HU = (μ_tissue − μ_water) / μ_water × 1000
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.
Which post-processing technique in CT creates a three-dimensional display by showing only the highest attenuation voxel along each line of sight?
Answer: Maximum intensity projection (MIP)
Maximum intensity projection (MIP) projects the highest HU value along each ray through the data, making it ideal for visualizing contrast-enhanced vessels and calcifications.
What is the significance of the CT dose index (CTDI) metric?
Answer: It quantifies the radiation output of a CT scanner for a standardized scan protocol
CTDI measures the scanner's radiation output in a standardized phantom and is used to characterize and compare dose output across protocols and scanners.