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Heat and Transient: Heat and transient are not classifications of cavitation.

Thermal and Mechanical: These terms refer to different bioeffects of ultrasound but are not types of cavitation.

Stable and Transient: These are the two types of cavitation observed in tissues during ultrasound. Stable cavitation involves the oscillation of gas bubbles without collapse, while transient cavitation involves the violent collapse of gas bubbles, which can generate high temperatures and shock waves.

Thermal and Stable: Thermal effects are a different concept related to tissue heating, not a type of cavitation.

Comprehensive and Detailed Explanation From Exact Extract:

At greater depths, pulse repetition frequency (PRF) is automatically reduced due to longer pulse travel times, lowering the Nyquist limit and increasing the likelihood of aliasing.

Principles and Instrumentation state:

"As sample depth increases, PRF decreases, lowering the Nyquist limit and increasing the risk of aliasing in pulsed-wave Doppler."

Doppler shift depends on flow velocity and angle, not depth.

Actual velocity measurements do not increase with depth.

Signal strength typically decreases (not increases) due to attenuation.

Therefore, the correct answer is A: Increased aliasing.

Increasing the pulse repetition frequency (PRF) helps to optimize the color Doppler imaging by reducing aliasing.

Aliasing occurs when the PRF is too low to accurately sample the rapid blood flow velocities, leading to incorrect color representation.

By increasing the PRF, the system can more accurately measure higher velocities without distortion, improving the overall quality of the color Doppler image.References:

ARDMS Sonography Principles and Instrumentation guidelines on Doppler imaging and techniques to reduce aliasing.

When sound waves encounter a smooth, flat surface, the primary interaction is reflection. This means the sound waves bounce back towards the transducer, producing echoes that are used to create the ultrasound image. Reflection is most effective when the surface is smooth and perpendicular to the sound beam, allowing for the maximum return of sound waves to the transducer.

ARDMS Sonography Principles and Instrumentation guidelines

Zagzebski, J. A. (1996). Essentials of Ultrasound Physics.

Comprehensive and Detailed Explanation From Exact Extract:

When evaluating high blood velocities, especially at angles closer to zero degrees (which produces maximum Doppler shifts), aliasing can easily occur because the Doppler frequency shift increases. To avoid aliasing, you must increase the Doppler scale (which increases the pulse repetition frequency, PRF) to accommodate these higher velocities.

According to sonography instrumentation references:

“The Doppler scale (PRF) must be increased when high velocities are anticipated to prevent aliasing, especially at optimal Doppler angles near zero degrees where maximum frequency shifts occur.”

Therefore, the correct answer is C: Increased Doppler scale settings.

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Axial resolution refers to the ability of an ultrasound system to distinguish between two structures that are close to each other along the path of the ultrasound beam. It is primarily determined by the spatial pulse length, which is the product of the wavelength and the number of cycles in a pulse. Shorter wavelengths result in shorter spatial pulse lengths, thereby improving axial resolution. This is because shorter wavelengths (which correspond to higher frequencies) allow for better differentiation between closely spaced structures along the beam's axis.

American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.

Comprehensive and Detailed Explanation From Exact Extract:

Low PRF reduces the Nyquist limit, making the system more susceptible to aliasing when Doppler shift frequencies exceed this limit.

Principles and Instrumentation state:

"Aliasing occurs when Doppler shifts exceed half the PRF (Nyquist limit). Lowering PRF increases aliasing susceptibility."

Spectral broadening (A) results from turbulence or poor angle.

Range ambiguity (B) occurs at high PRF.

Dropout (D) refers to signal loss, not aliasing.

Therefore, the correct answer is C: Aliasing.

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Comprehensive and Detailed Explanation From Exact Extract:

Axial resolution is determined by the spatial pulse length (SPL). A longer SPL means that structures closer together along the beam axis are more likely to overlap in the returning echoes, degrading axial resolution.

According to sonography instrumentation reference:

“Axial resolution is inversely related to spatial pulse length. Increasing SPL worsens the ability to distinguish closely spaced structures along the beam axis.”

Therefore, the correct answer is B: Degraded axial resolution.

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86

Based on the table in this image, what is the sensitivity?

A white square with black numbers and a white square with black numbers Description automatically generated

A. 32/33

B. 32/35

C. 45/46

D. 45/48

Answer: B

Comprehensive and Detailed Explanation From Exact Extract:

Sensitivity measures the test's ability to correctly identify true positives. It is calculated using the formula:

Sensitivity = True Positives / (True Positives + False Negatives)

From the table:

True Positives (TP) = 32 (Noninvasive test positive & Gold Standard positive)

False Negatives (FN) = 3 (Noninvasive test negative but Gold Standard positive)

Thus:

Sensitivity = 32 / (32 + 3)

Sensitivity = 32 / 35

According to sonography instrumentation reference:

“Sensitivity represents the proportion of actual positive cases correctly identified by the test.”

Therefore, the correct answer is B: 32/35.

At what Doppler angle to flow is the maximum Doppler shift frequency acquired?

A. 90 degrees

B. 60 degrees

C. 30 degrees

D. 0 degrees

Answer: D

Comprehensive and Detailed Explanation From Exact Extract:

The Doppler equation shows that the frequency shift is proportional to the cosine of the Doppler angle. The maximum value of cosine (cos 0° = 1) occurs at 0 degrees — meaning the beam is parallel to flow. At this angle, the full velocity component is measured.

According to sonography instrumentation reference:

“The maximum Doppler shift is obtained when the ultrasound beam is parallel (0 degrees) to blood flow.”

Therefore, the correct answer is D: 0 degrees.

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The placement of an echo on an ultrasound image is dependent on the assumption that the speed of sound in soft tissue is 1540 m/s. If the speed of sound in the medium is less than this assumed speed, the ultrasound system will interpret the returning echo as taking longer to return than it actually does. This causes the system to place the echo deeper in the image than its actual position. Therefore, the echo will be displayed "too deep" in the image.

Comprehensive and Detailed Explanation From Exact Extract:

The key advantage of pulsed wave Doppler is range resolution, meaning the operator can select a specific depth (sample volume) for measuring velocities. Continuous wave Doppler does not provide this capability, as it samples velocities along the entire beam path.

According to sonography instrumentation reference:

“Pulsed wave Doppler allows selection of sample volume depth, providing range resolution which continuous wave Doppler lacks.”

Therefore, the correct answer is B: Ability to select sample depth.

105

What adjustment is needed to optimize the image below?

A close-up of a medical scan Description automatically generated

A. Increase wall filter

B. Steer the box

C. Decrease scale

D. Raise focal zone

Answer: B

Comprehensive and Detailed Explanation From Exact Extract:

In the displayed image, the color box is not aligned parallel to the direction of blood flow in the vessel. Color Doppler is angle-dependent; when the color box is not properly steered to align with flow, the Doppler shift is reduced, and less color filling occurs. Steer the box to align the ultrasound beam more parallel to flow to maximize Doppler shift and improve color filling.

According to sonography instrumentation reference:

“Steering the color box aligns the Doppler beam with blood flow direction, optimizing the Doppler angle and improving flow visualization.”

Therefore, the correct answer is B: Steer the box.

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