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
Which type of CT detector converts X-ray photons directly into electrical charge using amorphous selenium?
Answer: Direct-conversion flat-panel detector
Direct-conversion detectors (e.g., amorphous selenium) convert X-rays directly to electrical charge without an intermediate light step, potentially improving spatial resolution.
Spectral CT using photon-counting detectors differs from energy-integrating detectors mainly because it:
Answer: Counts individual photons and records their energy levels
Photon-counting detectors register each photon individually and bin them by energy, enabling true spectral decomposition without energy overlap between bins.
In CT, the concept of 'noise power spectrum' (NPS) provides information about:
Answer: The frequency-dependent distribution of image noise
The NPS (or Wiener spectrum) describes how noise energy is distributed across spatial frequencies, capturing the texture and magnitude of noise in CT images.
Which reconstruction algorithm uses a statistical model of the imaging process to minimize a cost function iteratively, achieving better noise properties than FBP?
Answer: Maximum-likelihood expectation maximization (MLEM)
MLEM iteratively updates the image estimate to maximize the likelihood that the projection data would be observed given the current image, reducing noise and artifacts.
In helical CT, the 'pitch factor' is defined as table advancement per rotation divided by:
Answer: Total detector width (beam collimation)
Pitch = table feed per 360° rotation / total beam collimation width; a pitch of 1 means table advance equals the beam width with no overlap or gap.
The 'effective dose' in CT differs from absorbed dose (Gy) in that it accounts for:
Answer: Tissue weighting factors and radiation type
Effective dose (Sv) applies tissue weighting factors to equivalent doses in each organ, reflecting the overall stochastic risk to a standard individual from non-uniform irradiation.
Which CT image artifact results from inconsistent attenuation readings caused by rapid patient breathing during thoracic imaging?
Answer: Respiratory motion artifact
Respiratory motion during thoracic CT causes misregistration of lung boundaries and blurring of structures, classified as a motion artifact.