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MRI Pulse Sequences Flashcards

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

Read the first 6 MRI Pulse Sequences flashcards as text

  1. Which MRI technique measures cerebral blood flow and volume without contrast injection, using arterial water protons as an endogenous tracer?

    Answer: Arterial spin labeling (ASL)

    ASL uses RF pulses to magnetically label (invert) arterial blood water protons proximal to the imaging slab; labeled images are subtracted from control images to quantify cerebral perfusion.

  2. The echo time (TE) in gradient-echo sequences affects which type of contrast?

    Answer: T2* contrast — longer TE increases T2* weighting and susceptibility effects

    In gradient-echo sequences, TE controls T2* contrast; longer TE allows greater T2* dephasing, increasing susceptibility effects from blood products, iron, and air-tissue interfaces.

  3. Magnetization transfer (MT) contrast in MRI works by selectively saturating which proton pool?

    Answer: Bound protons in macromolecules (semisolid pool), which transfers saturation to free water

    An off-resonance RF pulse saturates the restricted macromolecular proton pool; saturation is transferred to free water through magnetization exchange, reducing the water signal proportional to MT ratio.

  4. Which k-space trajectory fills the center of k-space first, providing low-spatial-frequency (contrast) information early in the acquisition and reducing motion sensitivity?

    Answer: Centric (elliptic centric) k-space ordering

    Centric k-space ordering acquires the low-frequency center of k-space at the beginning of the scan, capturing image contrast during peak enhancement and minimizing motion effects on image quality.

  5. In MR imaging, the signal-to-noise ratio (SNR) improves with increasing field strength approximately as:

    Answer: Linearly (proportional to B0)

    SNR scales approximately linearly with B0 because both the equilibrium magnetization and the Larmor frequency (and thus the induced EMF) increase linearly with field strength.

  6. Which MRI sequence is the standard for evaluating the internal structure of bone marrow and is most sensitive to marrow infiltration or edema?

    Answer: STIR or fat-suppressed T2-weighted FSE

    STIR and fat-suppressed T2 sequences null normal fatty marrow signal, making pathological edema, infiltration, or tumor stand out as high signal against the nulled fat background.