Ultrasound Physics & Doppler Principles Flashcards

What is the approximate speed of sound in soft tissue used as the standard for ultrasound imaging?

Answer: 1,540 m/s

Most diagnostic ultrasound systems assume a propagation speed of 1,540 m/s in soft tissue.

The term 'wall filter' in Doppler ultrasound is used to eliminate signals from:

Answer: Slow-moving vessel walls and tissue

Wall filters (high-pass filters) remove low-frequency Doppler shifts caused by slow-moving vessel walls and surrounding tissue clutter.

When the angle of insonation is 0° in the Doppler equation, the cosine value is:

Answer: 1.0

cos(0°) = 1.0, meaning the beam is perfectly parallel to flow, yielding maximum Doppler frequency shift.

Which transducer design provides the best near-field resolution for superficial vascular structures like the carotid artery?

Answer: Linear array

Linear array transducers produce a rectangular field of view and superior near-field resolution ideal for superficial vessels.

Increasing the pulse repetition frequency (PRF) in pulsed Doppler will:

Answer: Increase the maximum detectable velocity

A higher PRF raises the Nyquist limit (PRF/2), allowing detection of higher velocities before aliasing occurs.

Acoustic shadowing behind a calcified plaque is caused by:

Answer: High acoustic impedance mismatch and attenuation by calcium

Calcium has very high acoustic impedance, causing strong reflection and absorption that prevents sound from reaching structures beyond it.

In spectral Doppler analysis, the spectral broadening index reflects:

Answer: The range of velocities present within the sample volume

Spectral broadening indicates a wide distribution of velocities within the sample volume, often associated with disturbed or turbulent flow.