Computed Tomography Science 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 Science flashcards as text
In CT scanner design, the gantry aperture refers to:
Answer: The opening through which the patient passes
The gantry aperture is the circular opening (typically 70–90 cm in diameter) through which the patient or object is positioned for scanning.
What is the primary purpose of the bow-tie (wedge) filter in a CT system?
Answer: To equalize photon flux across the detector array
The bow-tie filter attenuates the peripheral portion of the beam more than the center, equalizing photon fluence across the detector and reducing patient dose.
During a CT scan, tube current modulation (TCM) adjusts the mA based on:
Answer: Patient attenuation in real time
TCM reduces mA in less-attenuating regions (e.g., lungs) and increases it in denser regions (e.g., shoulders), optimizing dose while maintaining image quality.
The 'reconstruction kernel' (convolution filter) in CT primarily affects:
Answer: Spatial resolution and noise
Sharp kernels enhance spatial resolution but increase noise, while smooth kernels reduce noise at the cost of spatial resolution.
Which measure quantifies the overall radiation output of a CT scanner independent of scan length?
Answer: CTDI (CT Dose Index)
CTDI quantifies the radiation output of the CT scanner per rotation, independent of scan length, and is measured in mGy.
In iterative reconstruction (IR), image quality is improved compared to FBP primarily by:
Answer: Modeling noise and system physics to suppress artifacts
Iterative reconstruction uses repeated cycles that model photon statistics and system geometry to reduce noise and artifacts, often permitting lower-dose acquisitions.
Which scanning mode is most appropriate for imaging moving structures such as the heart in CT?
Answer: Prospective ECG-gated axial mode
Prospective ECG-gated axial acquisition triggers the scan at a specific cardiac phase, freezing motion and substantially reducing radiation dose compared to retrospective gating.