Practice Test Geeks(ARRT) American Registry of Radiologic Technologists Computed Tomography Certification Practice Test
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CT Physics Flashcards

7 cards from real ARRT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 CT Physics flashcards as text

  1. Size-specific dose estimate (SSDE) improves upon CTDIvol by:

    Answer: Incorporating patient size to provide a more accurate dose estimate for individual patients

    SSDE applies a conversion factor based on patient diameter or water equivalent diameter to CTDIvol, yielding a more patient-specific absorbed dose estimate.

  2. The primary interaction of diagnostic x-ray photons with soft tissue in CT is:

    Answer: Compton scattering

    At the diagnostic energy range used in CT (typically 80–140 kVp), Compton scattering is the dominant interaction in soft tissue.

  3. In multi-detector CT (MDCT), increasing the number of detector rows primarily allows:

    Answer: Simultaneous acquisition of more slices per rotation, improving z-axis coverage speed

    More detector rows mean more slice data acquired per rotation, covering a larger anatomical volume per gantry revolution and reducing scan time.

  4. Windowing in CT (setting window width and level) affects:

    Answer: Only the display of contrast by mapping HU values to gray shades

    Windowing is a display operation that maps selected HU ranges to the visible gray scale; it does not alter the underlying image data.

  5. What is the significance of the 'detector quantum efficiency' (DQE) in CT?

    Answer: It describes how efficiently the detector converts incident x-ray photons into useful signal

    DQE (or detective quantum efficiency) measures how well the detector captures and converts x-ray photons to signal, directly affecting dose efficiency and noise.

  6. Aliasing artifacts in CT most commonly occur due to:

    Answer: Insufficient angular sampling of projection data (undersampling)

    Aliasing arises when the sampling rate of projection views is too low to accurately represent fine detail, producing Moiré-like or streak patterns.

  7. The 'noise power spectrum' (NPS) in CT characterizes noise by:

    Answer: Describing how noise energy is distributed across spatial frequencies

    The NPS (or Wiener spectrum) describes the frequency distribution of noise variance, distinguishing coarse (low-frequency) from fine (high-frequency) noise textures.