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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. The term 'derated' intensity (e.g., ISPTA.3) in ultrasound safety refers to intensity that has been adjusted for:

    Answer: Assumed tissue attenuation of 0.3 dB/cm/MHz

    Derated values apply a standardized attenuation of 0.3 dB/cm/MHz to account for tissue absorption when reporting intensities in safety standards.

  2. Which statement about ultrasound bioeffects in diagnostic imaging is most accurate based on current evidence?

    Answer: No confirmed hazardous bioeffects exist at diagnostic levels, but prudent use is advised

    No independently confirmed hazardous bioeffects have been established at diagnostic exposure levels, yet prudent minimization of exposure (ALARA) remains the standard of care.

  3. Acoustic streaming in ultrasound refers to:

    Answer: Steady unidirectional fluid flow induced by acoustic radiation force

    Acoustic streaming is a mechanical bioeffect where sustained radiation pressure drives fluid in a net directional flow, independent of the Doppler effect.

  4. Which transducer characteristic most directly influences the potential for heating at the transducer face?

    Answer: Transducer efficiency (electroacoustic conversion)

    Poor electroacoustic conversion efficiency means more electrical energy is dissipated as heat at the transducer face rather than converted to acoustic energy.

  5. In the context of obstetric ultrasound, TIS (Soft Tissue Thermal Index) is preferred over TIB (Bone Thermal Index) during which trimester?

    Answer: First trimester, before ossification is significant

    TIS is used in the first trimester when fetal ossification is minimal; TIB becomes more relevant later when bone absorbs more ultrasound energy and heats significantly.

  6. Epidemiological studies of diagnostic ultrasound in pregnancy have consistently shown:

    Answer: No confirmed adverse outcomes at diagnostic exposure levels

    Large epidemiological studies have not identified adverse pregnancy outcomes attributable to diagnostic ultrasound exposure at clinical levels.

  7. Which factor does NOT increase the risk of thermally induced bioeffects during an ultrasound exam?

    Answer: Using harmonic imaging instead of fundamental frequency

    Harmonic imaging uses lower overall acoustic power and is generally considered safer thermally; in contrast, higher power, longer dwell time, and pre-existing fever all increase thermal risk.