ARDMS SPI Quality Assurance and Phantoms 3 — Questions and Answers
Question 1: A tissue-mimicking phantom contains hyperechoic spherical masses. These targets are primarily used to test which system performance parameter?
- Temporal resolution
- Dead zone depth
- Contrast resolution for high-reflectivity lesions (Correct answer)
- Doppler sensitivity
Correct answer: Contrast resolution for high-reflectivity lesions
Hyperechoic spherical targets surrounded by uniform background material test the system's ability to detect and resolve high-amplitude echoes against background speckle.
Question 2: Which QA measurement describes the shortest distance from the transducer face at which the system can display accurate image information?
- Depth of penetration
- Dead zone (Correct answer)
- Near field length
- Focal zone width
Correct answer: Dead zone
The dead zone is the region immediately adjacent to the transducer face where the system cannot detect echoes due to the ring-down artifact from the transmitted pulse.
Question 3: In a QA protocol for Doppler systems, a string phantom or flow phantom is used. What specific parameter does a string phantom test?
- Volume flow rate accuracy
- Velocity accuracy and angle dependence of Doppler measurements (Correct answer)
- Color flow sensitivity at depth
- Pulse repetition frequency calibration
Correct answer: Velocity accuracy and angle dependence of Doppler measurements
A string phantom moves a target at a known velocity, allowing the sonographer to verify that the system accurately reports Doppler-derived velocity at various beam-to-target angles.
Question 4: When assessing depth of penetration during QA, what endpoint is typically used to define maximum usable depth?
- The depth where frame rate drops below 15 Hz
- The deepest depth at which a uniform speckle pattern is still visible (Correct answer)
- The depth at which TGC compensation reaches maximum
- The point where the focal zone ends
Correct answer: The deepest depth at which a uniform speckle pattern is still visible
Penetration depth is defined as the greatest depth at which the speckle pattern from the tissue-mimicking material is still discernible above noise.
Question 5: A QA test finds that the dead zone has increased significantly from the baseline value. Which clinical implication is most important?
- Doppler measurements will overestimate velocity
- Superficial structures may not be visualized accurately (Correct answer)
- Color flow artifacts will increase
- Harmonic imaging will be impaired
Correct answer: Superficial structures may not be visualized accurately
An enlarged dead zone means structures immediately beneath the transducer face may be missed or misrepresented, which is critical for superficial examinations.
Question 6: Which of the following best explains why QA phantoms must be stored at a controlled temperature?
- Temperature changes alter the phantom's electrical impedance
- Speed of sound in the phantom changes with temperature, affecting distance accuracy (Correct answer)
- Phantom radioactivity increases at higher temperatures
- Color dyes in the phantom degrade above 25°C
Correct answer: Speed of sound in the phantom changes with temperature, affecting distance accuracy
The speed of sound in phantom material is temperature-dependent; significant deviation from calibration temperature changes the apparent distances of internal targets.
Question 7: Which transducer performance defect is most likely to produce a focal band of absent or reduced echoes at a specific depth in a QA phantom image?
- Cracked transducer housing
- A dead row of elements in a 1.5D array (Correct answer)
- Excessive coupling gel
- Incorrect TGC slope
Correct answer: A dead row of elements in a 1.5D array
A dead row of elements in a multidimensional array creates a shadow band or region of signal dropout at the depth where that row's contribution is critical.
ARDMS SPI Quality Assurance and Phantoms 3
A tissue-mimicking phantom contains hyperechoic spherical masses.
These targets are primarily used to test which system performance parameter?