Computed Tomography Ultimate 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 Ultimate flashcards as text
What is the purpose of 'prospective triggering' in cardiac CT?
Answer: To acquire data only during a specific, predetermined phase of the cardiac cycle
Prospective triggering uses the ECG signal to trigger X-ray exposure only during a specific quiescent phase, significantly reducing radiation dose compared to retrospective gating.
Which ionizing radiation unit is used to express the effective dose that accounts for tissue radiosensitivity?
Answer: Sievert (Sv)
The Sievert (Sv) is used to express effective dose, which weights absorbed dose by tissue-specific radiation sensitivity and radiation type weighting factors.
In CT angiography, what is the bolus tracking technique used for?
Answer: Triggering the diagnostic scan when contrast reaches the target vessel
Bolus tracking monitors contrast enhancement in a target vessel using repeated low-dose images and automatically triggers the diagnostic scan when the preset HU threshold is reached.
What is the main disadvantage of increasing pitch in helical CT?
Answer: Reduced z-axis resolution
Higher pitch values interpolate data across a wider z-axis distance, which degrades longitudinal (z-axis) spatial resolution and can increase image noise.
What type of CT artifact is caused by patient movement during data acquisition?
Answer: Motion artifact
Motion artifacts appear as blurring, streaks, or ghosting on images when the patient moves during the scan, causing inconsistent projection data.
Which window setting is most appropriate for evaluating pulmonary nodules on chest CT?
Answer: Lung window (W:1500, L:-600)
Lung window settings use a wide window width and low center level to display the full dynamic range of pulmonary parenchyma including subtle nodules and airways.
What is the primary determinant of contrast-to-noise ratio (CNR) in CT imaging?
Answer: Radiation dose
Radiation dose is the primary determinant of CNR because higher dose reduces quantum noise, making differences in tissue attenuation more detectable.