MCQ Flashcards

What happens to the ultrasound beam at an interface where the angle of incidence equals the critical angle?

Answer: Refraction bends the beam to 90°

At the critical angle, refraction causes the transmitted beam to travel along the interface at 90°, and total internal reflection occurs.

Which Doppler mode provides the best sensitivity for detecting slow-flow states such as organ perfusion?

Answer: Power Doppler

Power Doppler displays the amplitude (power) of the Doppler signal and is more sensitive to slow flow than color or pulsed wave Doppler.

In B-mode imaging, increasing the time gain compensation (TGC) at depth primarily compensates for:

Answer: Attenuation of the ultrasound beam

TGC amplifies returning echoes from deeper structures to compensate for the progressive attenuation of the beam as it travels through tissue.

A resistive index (RI) value close to 1.0 in a renal artery waveform suggests:

Answer: Absent or reversed diastolic flow

An RI near 1.0 indicates minimal or absent end-diastolic flow, suggesting markedly elevated distal resistance.

Which statement best describes lateral resolution in ultrasound?

Answer: It is determined by beam width perpendicular to the beam axis

Lateral resolution depends on beam width; the narrower the beam at a given depth, the better the lateral resolution.

In M-mode echocardiography, what does the vertical axis represent?

Answer: Depth (distance from transducer)

In M-mode, the vertical axis shows depth from the transducer while the horizontal axis represents time.

Which material property most determines the acoustic impedance of a tissue?

Answer: Density and speed of sound

Acoustic impedance (Z) is the product of tissue density (ρ) and the speed of sound (c): Z = ρc.