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. A 'ring artifact' in CT is most commonly caused by:

    Answer: A malfunctioning or miscalibrated detector element

    Ring artifacts form concentric circles centered on the scanner's isocenter when one or more detector channels give consistently incorrect readings.

  2. In CT, the modulation transfer function (MTF) is used to characterize:

    Answer: Spatial frequency response and limiting spatial resolution

    The MTF describes how well the CT system transfers spatial frequencies from object to image, defining the system's spatial resolution capability.

  3. Increasing the x-ray tube voltage (kVp) in CT primarily results in:

    Answer: Higher mean photon energy and reduced photoelectric interactions

    Higher kVp produces a higher mean photon energy beam with greater penetrating power; Compton scatter dominates over photoelectric effect, reducing subject contrast.

  4. What is the main clinical use of dual-energy CT (DECT)?

    Answer: Material decomposition to differentiate tissue composition (e.g., iodine vs. calcium)

    DECT acquires data at two different kVp levels; the difference in attenuation at each energy allows material decomposition to characterize tissue composition.

  5. The 'partial volume effect' artifact in CT occurs when:

    Answer: A voxel contains two or more tissues of different attenuation, producing an averaged HU value

    Partial volume averaging occurs when a single voxel spans structures of different densities, and the CT number represents the average rather than any single material.

  6. In CT, 'DLP' (dose-length product) is calculated as:

    Answer: CTDIvol × scan length

    DLP = CTDIvol × scan length (cm); it estimates the total energy deposited in the patient and is used to calculate effective dose.

  7. Which phenomenon explains why CT numbers for bone may appear elevated at the center of a thick bony structure compared to peripheral bone?

    Answer: Beam hardening cupping artifact

    Beam hardening causes preferential absorption of lower-energy photons; more hardening occurs centrally, leading to erroneously high CT numbers at bone edges and low values centrally (cupping).