Attenuation, Reflection, and Refraction Flashcards

Acoustic shadowing distal to a gallstone is primarily due to:

Answer: High attenuation and reflection by the calcified stone

Gallstones strongly reflect and absorb sound, leaving a shadow of reduced echo amplitude posterior to the stone.

Which property of a medium directly determines whether refraction will occur at an oblique interface?

Answer: Propagation speed

Refraction depends on differing propagation speeds in adjacent media, not on their impedances.

The average propagation speed of sound in soft tissue used by ultrasound systems is:

Answer: 1540 m/s

Ultrasound machines assume a propagation speed of 1540 m/s in soft tissue for depth calculations.

Non-specular (diffuse) reflectors differ from specular reflectors in that they:

Answer: Scatter sound in many directions regardless of beam angle

Non-specular (diffuse) reflectors have irregular or small surfaces that scatter sound in all directions, making them angle-independent.

Which factor does NOT directly affect the intensity reflection coefficient at a tissue interface?

Answer: Transducer frequency

At normal incidence, the reflection coefficient depends only on the two media's acoustic impedances, not on frequency.

Increasing the depth of imaging requires using a lower frequency primarily because:

Answer: Lower frequencies undergo less attenuation per centimeter

Attenuation per centimeter decreases with lower frequency, allowing sound to penetrate deeper into tissue.

Which of the following best describes the transmission coefficient when sound passes from one medium to another?

Answer: It equals 1 minus the reflection coefficient

Conservation of energy requires that the transmission coefficient T = 1 − R, where R is the reflection coefficient.