ARDMS SPI Principles of Image Resolution 3 — Questions and Answers
Question 1: Which statement about dynamic receive focusing is correct?
- It transmits multiple focal beams simultaneously
- It adjusts the receive focus continuously as echoes return from increasing depths (Correct answer)
- It is the same as transmit focusing
- It only applies to elevation focusing
Correct answer: It adjusts the receive focus continuously as echoes return from increasing depths
Dynamic receive focusing updates the receive delays in real time so the system is always focused at the depth from which echoes are currently arriving.
Question 2: The quality factor (Q factor) of a transducer is defined as:
- Operating frequency divided by bandwidth (Correct answer)
- Bandwidth divided by operating frequency
- Pulse length times frequency
- Amplitude at resonance divided by input power
Correct answer: Operating frequency divided by bandwidth
Q = operating frequency / bandwidth; a lower Q factor indicates a wider bandwidth and better axial resolution.
Question 3: Grating lobes degrade image quality primarily by causing:
- Increased axial resolution
- Artifactual echoes from off-axis structures appearing in the main image (Correct answer)
- Improved lateral resolution at depth
- Reduced frame rate
Correct answer: Artifactual echoes from off-axis structures appearing in the main image
Grating lobes are secondary beams that return echoes from off-axis targets, producing artifacts in the image.
Question 4: Which aperture change improves lateral resolution for a linear array?
- Decreasing the active aperture
- Increasing the active aperture (Correct answer)
- Using fewer elements
- Reducing frequency
Correct answer: Increasing the active aperture
A larger aperture creates a more tightly focused beam, improving lateral resolution.
Question 5: At the near field (Fresnel zone) boundary, the beam diameter is approximately:
- Equal to the transducer radius
- Twice the transducer diameter
- Half the transducer diameter (Correct answer)
- Equal to the wavelength
Correct answer: Half the transducer diameter
At the last axial maximum (near-field/far-field boundary), the beam width is approximately half the transducer diameter.
Question 6: Which mode of ultrasound provides the best temporal resolution?
- 2D B-mode with many focal zones
- M-mode (Correct answer)
- 3D volume imaging
- Color Doppler
Correct answer: M-mode
M-mode interrogates a single line of sight repeatedly at very high rates, giving the best temporal resolution.
Question 7: Axial resolution is most correctly defined as the minimum distance between two reflectors that can be distinguished along:
- The width of the beam
- The direction of beam propagation (Correct answer)
- The elevation plane
- The Doppler axis
Correct answer: The direction of beam propagation
Axial resolution separates targets along the direction of sound travel, determined by spatial pulse length.
ARDMS SPI Principles of Image Resolution 3
Which statement about dynamic receive focusing is correct?