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Ultrasound Bioeffects and Safety 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 index displayed on modern ultrasound systems specifically relates to the risk of acoustic cavitation?

    Answer: Mechanical Index (MI)

    The Mechanical Index (MI) quantifies the likelihood of cavitation by comparing peak negative pressure to the square root of frequency.

  2. Stable cavitation differs from inertial cavitation in that stable cavitation involves:

    Answer: Bubbles oscillating in a sustained, non-destructive manner

    Stable (non-inertial) cavitation describes gas bubbles that oscillate repetitively without collapsing, whereas inertial cavitation involves violent implosion.

  3. The ALARA principle in diagnostic ultrasound means the operator should:

    Answer: Use the lowest output that still yields diagnostic information

    ALARA (As Low As Reasonably Achievable) requires minimizing acoustic exposure while still obtaining the necessary diagnostic image quality.

  4. Which ultrasound mode typically produces the highest time-averaged acoustic intensity and greatest potential for thermal bioeffects?

    Answer: Pulsed-wave Doppler

    Pulsed-wave Doppler has a high duty factor and focuses the beam on a small sample volume, resulting in the highest time-averaged intensity and greatest heating potential.

  5. A Thermal Index value of 2.0 indicates that the ultrasound system is capable of raising tissue temperature by approximately:

    Answer: 2.0°C

    The TI is defined as the ratio of acoustic power to the power needed to raise tissue temperature by 1°C, so TI = 2.0 suggests a potential 2°C rise.

  6. During a first-trimester obstetric exam, which combination of indices represents the greatest concern for bioeffects?

    Answer: High MI, high TI

    Both a high MI (cavitation risk) and high TI (thermal risk) together represent maximal bioeffect potential and should be minimized during embryonic development.

  7. Which biological tissue is considered MOST sensitive to the thermal effects of diagnostic ultrasound?

    Answer: Developing embryonic/fetal tissue

    Developing embryonic and fetal tissues are most sensitive to thermal bioeffects because rapidly dividing cells have lower heat tolerance and reduced repair capacity.