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
The Nyquist theorem in CT states that to accurately represent a spatial frequency, the sampling rate must be at least:
Answer: Twice the frequency of interest
The Nyquist criterion requires a sampling frequency at least twice the highest spatial frequency to avoid aliasing artifacts in the reconstructed image.
What is the primary advantage of dual-energy CT (DECT) over single-energy CT?
Answer: Material decomposition and iodine quantification
DECT acquires data at two different kVp levels, enabling material decomposition to identify and quantify iodine, calcium, uric acid, and other substances.
Quantum noise in CT images is primarily a function of:
Answer: The number of photons reaching the detector
Quantum (photon) noise arises from statistical fluctuations in photon counts; fewer photons (low mAs or high attenuation) result in increased noise.
In CT, the term 'z-axis resolution' refers to resolution along which dimension?
Answer: Superior-to-inferior patient axis
The z-axis is the longitudinal axis running head-to-foot along the patient, and z-axis resolution determines the ability to distinguish structures in that direction.
Which factor primarily determines the minimum slice thickness achievable in a multi-detector CT system?
Answer: Individual detector element width in the z-direction
The detector element width in the z-axis sets the minimum detector aperture and therefore the thinnest slice that can be acquired.
In CT image quality assessment, the modulation transfer function (MTF) is used to evaluate:
Answer: Spatial resolution as a function of spatial frequency
The MTF describes how faithfully the CT system reproduces contrast at various spatial frequencies, characterizing the system's spatial resolution capability.
The partial volume effect in CT produces inaccurate HU values when:
Answer: Structures of different densities share the same voxel
When a voxel contains tissues of different densities, the displayed HU is a weighted average, potentially misrepresenting the true attenuation of each component.