ARDMS SPI MCQ 5 — Questions and Answers
Question 1: Which property of ultrasound contrast agents (microbubbles) makes them effective Doppler signal enhancers?
- Their high acoustic impedance similar to bone
- Their strong non-linear oscillation and backscatter at diagnostic pressures (Correct answer)
- Their ability to absorb all ultrasound energy
- Their large size relative to red blood cells
Correct answer: Their strong non-linear oscillation and backscatter at diagnostic pressures
Microbubbles oscillate non-linearly under ultrasound pressure, producing strong harmonic backscatter that greatly enhances Doppler signals.
Question 2: What does the term 'dynamic range' refer to in ultrasound imaging?
- The range of Doppler velocities the system can display
- The ratio of the largest to smallest signal amplitudes the system can process (Correct answer)
- The depth range over which focus is maintained
- The range of frequencies emitted by the transducer
Correct answer: The ratio of the largest to smallest signal amplitudes the system can process
Dynamic range is the ratio (in dB) between the maximum and minimum signal amplitudes that the system can detect and display.
Question 3: In a spectral Doppler waveform, spectral broadening refers to:
- An increase in peak systolic velocity
- Widening of the frequency band representing a range of flow velocities within the sample volume (Correct answer)
- Aliasing wrapping the waveform below baseline
- Increased pulsatility of the waveform
Correct answer: Widening of the frequency band representing a range of flow velocities within the sample volume
Spectral broadening occurs when multiple velocities are present in the sample volume, widening the spectral window and filling in the clear area beneath the waveform envelope.
Question 4: The ALARA principle in diagnostic ultrasound instructs operators to:
- Always use maximum power for best image quality
- Keep acoustic output as low as reasonably achievable while obtaining diagnostic information (Correct answer)
- Limit scanning time to no more than 5 minutes per session
- Avoid Doppler modes in all obstetric exams
Correct answer: Keep acoustic output as low as reasonably achievable while obtaining diagnostic information
ALARA (As Low As Reasonably Achievable) requires using the minimum acoustic output necessary to obtain clinically useful images.
Question 5: Which of the following correctly describes the relationship between frequency and penetration depth in ultrasound?
- Higher frequency provides greater depth penetration
- Lower frequency provides greater depth penetration (Correct answer)
- Frequency has no effect on penetration
- Higher frequency always improves resolution at all depths equally
Correct answer: Lower frequency provides greater depth penetration
Lower frequency ultrasound attenuates less per centimeter of tissue, allowing greater penetration depth at the cost of reduced resolution.
Question 6: Acoustic shadowing posterior to a gallstone occurs because the stone:
- Reflects and absorbs most of the incident ultrasound, leaving reduced energy beyond it (Correct answer)
- Speeds up the ultrasound beam causing registration errors
- Creates reverberation that fills the posterior region with echoes
- Bends the beam away from its original path
Correct answer: Reflects and absorbs most of the incident ultrasound, leaving reduced energy beyond it
Gallstones strongly reflect and absorb ultrasound, resulting in little energy passing through to generate echoes posterior to the stone.
Question 7: In continuous wave (CW) Doppler, which limitation is NOT present in pulsed wave Doppler?
- Range ambiguity (cannot localize signal depth) (Correct answer)
- Aliasing at high velocities
- Dependence on Doppler angle for accurate velocity measurement
- Wall filter requirement
Correct answer: Range ambiguity (cannot localize signal depth)
CW Doppler uses simultaneous transmit and receive crystals and cannot determine the depth of origin of Doppler signals, causing range ambiguity.
ARDMS SPI MCQ 5
Which property of ultrasound contrast agents (microbubbles) makes them effective Doppler signal enhancers?