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Transducer Construction and Function Flashcards

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

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  1. Which of the following BEST describes the piezoelectric effect as used in diagnostic ultrasound transducers?

    Answer: Conversion of electrical energy to mechanical energy and vice versa

    The piezoelectric effect allows certain crystals to convert electrical signals into mechanical (acoustic) vibrations and incoming pressure waves back into electrical signals.

  2. A phased array transducer steers and focuses the beam primarily by adjusting:

    Answer: Time delays applied to individual element firings

    Phased arrays use programmable electronic time delays across all elements to steer and dynamically focus the beam in real time.

  3. Increasing the diameter of a single-element unfocused transducer will:

    Answer: Increase the near-field length

    Near-field length = r²/λ; a larger radius (r) increases the near-field length, keeping the beam collimated for a longer distance.

  4. Side lobes in ultrasound transducers are most problematic because they:

    Answer: Create artifact echoes that appear to originate from the main beam

    Side lobes radiate energy off-axis; reflectors in their path produce echoes that the system incorrectly places along the main beam axis, creating artifacts.

  5. What distinguishes grating lobes from side lobes in array transducers?

    Answer: Grating lobes arise from the periodic spacing of array elements, not from the element aperture

    Grating lobes result from constructive interference due to the regular inter-element spacing of array transducers, while side lobes are inherent to any finite aperture.

  6. The resonant frequency of a piezoelectric crystal is primarily determined by its:

    Answer: Thickness

    Resonant frequency is inversely proportional to crystal thickness: f = c / 2t, where c is the propagation speed within the crystal.

  7. Which transducer type provides the SMALLEST footprint and is therefore best suited for cardiac imaging between rib spaces?

    Answer: Phased array

    The phased array has a small footprint that fits between ribs and uses electronic steering to produce a wide sector image from that small window.