ARDMS SPI - Sonography Principles and Instrumentation

Comprehensive and Detailed Explanation From Exact Extract:

Damping reduces the number of cycles per pulse, shortening pulse duration and spatial pulse length, which directly improves axial resolution.

Principles and Instrumentation:

"Axial resolution improves with shorter spatial pulse length, achieved by damping, which limits ringing of the transducer."

Lateral resolution (A) depends on beam width.

Contrast resolution (B) relates to dynamic range.

Temporal resolution (C) is tied to frame rate.

Therefore, the correct answer is D: Axial.

Comprehensive and Detailed Explanation From Exact Extract:

Aliasing occurs when the Doppler shift exceeds the Nyquist limit, which is directly tied to pulse repetition frequency (PRF), represented on the machine as Doppler scale. A Doppler scale set too low reduces the Nyquist limit, making aliasing more likely.

According to sonography instrumentation reference:

“Aliasing occurs when Doppler scale (PRF) is set too low relative to the measured velocities, causing signal wrap-around.”

Therefore, the correct answer is B: Doppler scale too low.

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Comprehensive and Detailed Explanation From Exact Extract:

Continuous wave (CW) Doppler can measure very high velocities without aliasing because it does not have a Nyquist limit like pulsed-wave Doppler.

Principles and Instrumentation state:

"Aliasing is eliminated in continuous wave Doppler since it does not rely on sampling and has no upper velocity limit."

Output power (A) affects signal strength, not aliasing.

Higher frequency (B) increases aliasing susceptibility.

Decreasing PRF (C) actually worsens aliasing.

Therefore, the correct answer is D: Using continuous wave Doppler ultrasound.

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Comprehensive and Detailed Explanation From Exact Extract:

A larger sample volume collects Doppler signals from a wider region, which can include multiple velocities and noise. This leads to a broader spectrum (spectral broadening) and may introduce additional noise into the signal.

According to sonography instrumentation reference:

“Increasing the sample volume size increases the likelihood of including multiple velocity components and noise, resulting in spectral broadening and reduced spectral clarity.”

Therefore, the correct answer is B: Increased noise.

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Comprehensive and Detailed Explanation From Exact Extract:

Defects in transducer crystals result in missing or weakened signals along the beam path produced by those elements, creating dropout. In array transducers, dropout typically appears as vertical or horizontal dark zones depending on which elements are affected.

According to sonography instrumentation reference:

“Crystal failure results in areas of signal dropout directly beneath the defective elements due to loss of transmitted or received signals.”

Therefore, the correct answer is D: Dropout.

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Comprehensive and Detailed Explanation From Exact Extract:

Higher frequencies are more attenuated than lower frequencies. When scanning calcified structures, increasing the frequency enhances attenuation, which makes posterior shadowing more pronounced and visible.

According to sonography instrumentation reference:

“Increasing frequency increases attenuation, thereby enhancing acoustic shadowing posterior to highly attenuating structures such as calcifications or bone.”

Therefore, the correct answer is D: Frequency.

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