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Acoustic Waves and Properties 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 tissue type has the highest acoustic propagation speed?

    Answer: Bone

    Bone has the highest stiffness among listed tissues, giving it the greatest propagation speed (~3500 m/s).

  2. Specular reflection occurs when sound strikes a boundary that is:

    Answer: Large and smooth relative to the wavelength

    Specular reflectors are large, flat, smooth surfaces that reflect sound at an angle equal to the incident angle, like a mirror.

  3. Attenuation of ultrasound in soft tissue is approximately:

    Answer: 0.5 dB/cm/MHz

    The standard approximation for attenuation in soft tissue is 0.5 dB/cm/MHz, used clinically for TGC calculations.

  4. Scattering of ultrasound is most likely to occur when the reflecting structure is:

    Answer: Similar in size or smaller than the wavelength

    Non-specular (diffuse) scattering occurs when reflectors are small relative to wavelength, producing omnidirectional echoes used in gray-scale imaging.

  5. When sound passes from a medium with low acoustic impedance to one with high acoustic impedance, the reflected wave will have:

    Answer: A phase shift of 180°

    Reflection at an interface where impedance increases causes a 180° phase reversal (pressure inversion) of the reflected wave.

  6. The decibel (dB) scale is used in ultrasound because:

    Answer: It simplifies multiplication of intensities into addition

    The logarithmic dB scale converts large multiplicative intensity ratios into manageable additive numbers, matching human perception of loudness.

  7. Which of the following is NOT a mechanism of ultrasound attenuation in tissue?

    Answer: Refraction

    Refraction redirects the beam but does not remove energy from it, so it is not an attenuation mechanism; absorption, reflection, and scattering all reduce beam intensity.