ARDMS SPI MCQ 3 — Questions and Answers
Question 1: What happens to the ultrasound beam at an interface where the angle of incidence equals the critical angle?
- Total reflection occurs
- Refraction bends the beam to 90° (Correct answer)
- Complete transmission with no reflection
- The beam is absorbed entirely
Correct 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.
Question 2: Which Doppler mode provides the best sensitivity for detecting slow-flow states such as organ perfusion?
- Continuous wave Doppler
- Pulsed wave Doppler
- Power Doppler (Correct answer)
- Color flow Doppler
Correct 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.
Question 3: In B-mode imaging, increasing the time gain compensation (TGC) at depth primarily compensates for:
- Refraction artifact
- Attenuation of the ultrasound beam (Correct answer)
- Aliasing in Doppler
- Grating lobe formation
Correct 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.
Question 4: A resistive index (RI) value close to 1.0 in a renal artery waveform suggests:
- Normal low-resistance flow
- High diastolic flow
- Absent or reversed diastolic flow (Correct answer)
- Elevated systolic velocity only
Correct answer: Absent or reversed diastolic flow
An RI near 1.0 indicates minimal or absent end-diastolic flow, suggesting markedly elevated distal resistance.
Question 5: Which statement best describes lateral resolution in ultrasound?
- It is determined by pulse length along the beam axis
- It is determined by beam width perpendicular to the beam axis (Correct answer)
- It improves with lower frequency transducers
- It is independent of depth
Correct 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.
Question 6: In M-mode echocardiography, what does the vertical axis represent?
- Time
- Depth (distance from transducer) (Correct answer)
- Velocity
- Frequency shift
Correct answer: Depth (distance from transducer)
In M-mode, the vertical axis shows depth from the transducer while the horizontal axis represents time.
Question 7: Which material property most determines the acoustic impedance of a tissue?
- Temperature and viscosity
- Density and speed of sound (Correct answer)
- Attenuation coefficient alone
- Absorption and scattering ratio
Correct answer: Density and speed of sound
Acoustic impedance (Z) is the product of tissue density (ρ) and the speed of sound (c): Z = ρc.
ARDMS SPI MCQ 3
What happens to the ultrasound beam at an interface where the angle of incidence equals the critical angle?