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Imaging Systems Flashcards

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

Read the first 7 Imaging Systems flashcards as text

  1. Which nuclear medicine imaging modality provides functional 3D images by detecting pairs of annihilation photons?

    Answer: PET

    PET (Positron Emission Tomography) detects coincident 511 keV annihilation photons produced when a positron meets an electron, enabling 3D functional imaging.

  2. In ultrasound imaging, axial resolution is primarily determined by:

    Answer: Transducer frequency and pulse length

    Axial resolution (along the beam direction) depends on the spatial pulse length, which is determined by the transducer frequency and the number of cycles per pulse.

  3. A CT system's ability to distinguish between two objects of similar density is described by which performance metric?

    Answer: Low-contrast detectability

    Low-contrast detectability (or contrast resolution) describes the system's ability to differentiate structures with small differences in X-ray attenuation.

  4. The ALARA principle as applied to ionizing radiation imaging means:

    Answer: As Low As Reasonably Achievable

    ALARA (As Low As Reasonably Achievable) is the radiation protection philosophy of minimizing patient and staff dose while still obtaining diagnostic quality images.

  5. In MRI, the T2* relaxation time differs from T2 because T2* also accounts for:

    Answer: Magnetic field inhomogeneities and susceptibility effects

    T2* (T2-star) is shorter than T2 because it incorporates both true spin-spin relaxation and additional dephasing from local magnetic field inhomogeneities.

  6. Which type of X-ray detector directly converts X-ray photons to electrical charge without an intermediate light conversion step?

    Answer: Amorphous selenium flat-panel detector

    Amorphous selenium (a-Se) flat-panel detectors are direct conversion detectors; X-ray photons liberate charge carriers directly in the selenium layer without producing light.

  7. What is the main clinical advantage of SPECT over planar gamma camera imaging?

    Answer: Elimination of depth-dependent overlapping structures

    SPECT acquires projections from multiple angles to reconstruct 3D tomographic slices, eliminating the superimposition of overlying and underlying structures that limits planar imaging.