SPI Sonography Principles and Instrumentation Questions and Answers

Enhancement is an artifact that results from decreased attenuation. When an ultrasound wave travels through a medium with lower attenuation compared to surrounding tissues, it loses less energy. Consequently, the structures located deeper than the low-attenuation medium appear brighter on the ultrasound image. This artifact is commonly observed behind fluid-filled structures, such as cysts or the urinary bladder, where the sound waves encounter minimal resistance and thus less attenuation.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Diagnostic Ultrasound: Principles and Instruments" by Frederick W. Kremkau

Temporal resolution is improved by increasing the frame rate. One way to increase the frame rate is by decreasing the packet size (also known as ensemble length) in color Doppler imaging. The packet size refers to the number of pulses used to determine the Doppler shift at each location. A smaller packet size means fewer pulses are required, which allows for quicker data acquisition and thus a higher frame rate. Increasing the field of view, decreasing transmit frequency, and increasing line density would all decrease the frame rate and thus degrade temporal resolution.

The color Doppler image shows an artifact where high-velocity blood flow exceeds the Nyquist limit, resulting in color wrap-around or aliasing. This artifact is visualized as a mosaic pattern of colors that abruptly change, indicating that the velocity exceeds the color Doppler scale's maximum. Aliasing occurs when the sampling rate (pulse repetition frequency) is insufficient to accurately capture the high velocities, causing the display to cycle back to lower velocities.

Refraction is the change in direction of a sound wave as it crosses a boundary between two different tissues at an oblique angle, where there is a difference in propagation speeds between the tissues. This bending of the sound wave path occurs due to the change in speed, causing the wave to change direction according to Snell's law. Refraction can result in artifacts such as edge shadowing and displacement of structures in an ultrasound image.

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:

As frequency increases, attenuation (energy loss due to absorption, scattering, and reflection) also increases. This limits penetration but improves resolution for superficial structures.

According to sonography instrumentation reference:

“Attenuation increases directly with frequency, limiting penetration but enhancing resolution in superficial imaging.”

Therefore, the correct answer is C: Attenuation.

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Comprehensive and Detailed Explanation From Exact Extract:

In color Doppler, frequency shifts can be displayed either above or below the baseline in spectral Doppler. In spectral Doppler, a positive shift is displayed above the baseline by default (unless inverted). In color Doppler, red/blue assignments depend on color map orientation.

Principles and Instrumentation state:

"A positive Doppler shift (flow toward the transducer) is displayed above the baseline in spectral Doppler."

Red color (B) does not always correspond to positive shift; it depends on color map.

Negative shift (C) does not always indicate venous flow.

Wall filter settings (D) affect low-velocity signals, not shift direction.

Therefore, the correct answer is A: A positive shift is always above the baseline.

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In the tissue-mimicking phantom image, Option D (blue box) is used to evaluate transverse distance measurement accuracy. Phantoms are used to simulate human tissue and provide a standardized way to test the accuracy and precision of ultrasound machines. Transverse distance measurement accuracy is assessed by measuring known distances between targets in the phantom. The blue box (Option D) typically contains targets positioned to specifically test the accuracy of transverse measurements, ensuring that the ultrasound system provides reliable and precise distance readings.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

"Quality Assurance for Ultrasound Imaging Systems" by AAPM (American Association of Physicists in Medicine)

The aperture of a transducer is the active area that emits and receives the ultrasound waves. In a linear array transducer, increasing the aperture (using more elements for transmission and reception) results in a deeper focus because the beam is more tightly focused over a longer distance. This improves lateral resolution at greater depths, as the ultrasound beam maintains a narrower width for a longer distance. It allows for better imaging of deeper structures without sacrificing resolution.

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

The primary difference between Image A and Image B is the overall gain setting. Gain controls the amplification of the received echoes. A lower gain setting results in a darker image with less overall brightness, which is evident in Image A compared to Image B. Image B appears brighter, indicating a higher gain setting that amplifies the echoes more, making the structures appear more prominently.

ARDMS Sonography Principles and Instrumentation guidelines

Hedrick, W. R., Hykes, D. L., & Starchman, D. E. (2005).Ultrasound Physics and Instrumentation.

Comprehensive and Detailed Explanation From Exact Extract:

Continuous wave (CW) Doppler utilizes two separate crystals: one constantly transmitting and one constantly receiving. This setup allows CW Doppler to measure very high velocities without aliasing, but at the cost of losing range specificity (no depth resolution).

According to sonography instrumentation reference:

“Continuous wave Doppler uses two separate elements for continuous transmission and reception of sound waves, allowing for detection of very high velocities but without depth specificity.”

Therefore, the correct answer is D: Dedicated transmit and receive crysta

82

What artifact is indicated by the arrows in the image below?

An ultrasound image of a fetus Description automatically generated

A. Ring down

B. Grating lobe

C. Enhancement

D. Refraction

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

The image shows a bright, continuous, vertical band extending from a gas-containing structure (seen at the top). This is characteristic of ring down artifact, which occurs when multiple small gas bubbles resonate and create continuous echoes below the structure.

According to sonography instrumentation reference:

“Ring down artifact results from resonance of gas bubbles, producing a continuous series of echoes distal to the source. It appears as a bright, vertical band that does not fade with depth.”

Therefore, the correct answer is A: Ring down.

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Increased Transmit Frequency: This would generally improve the resolution of the image but does not directly correlate to the changes seen in the provided image link.

Increased Scale: Adjusting the scale changes the velocity range displayed but does not directly affect the speckle or noise reduction.

Decreased Color Gain: Reducing the color gain can decrease the amount of color noise, making the blood flow regions more defined, which aligns with the change observed from image A to image B.

Decreased Acoustic Power: This reduces the overall intensity of the ultrasound beam, affecting penetration depth and overall brightness but is less likely to result in the specific improvements seen.

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.

The Doppler shift is highest when the angle between the ultrasound beam and the direction of blood flow is 0 degrees. This is because the cosine of 0 degrees is 1, maximizing the Doppler frequency shift. As the angle increases towards 90 degrees, the cosine value decreases, reducing the Doppler shift.

ARDMS Sonography Principles and Instrumentation guidelines

Hoskins, P. R., Thrush, A., Martin, K., & Whittingham, T. A. (2010). Diagnostic Ultrasound: Physics and Equipment.

Comprehensive and Detailed Explanation From Exact Extract:

Write magnification acquires new data over the smaller field of view with a higher number of scan lines, improving spatial resolution.

Principles and Instrumentation state:

"Write magnification rescans the selected region with new data acquisition, increasing the number of pixels and improving resolution."

Post-processing (A) applies to read magnification.

Larger pixel size (C) would decrease resolution.

Write magnification improves, not decreases (D), spatial resolution.

Therefore, the correct answer is B: New data acquisition.

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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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Comprehensive and Detailed Explanation From Exact Extract:

Using multiple focal zones improves lateral resolution but requires additional time for each focal zone acquisition, which reduces frame rate and therefore degrades temporal resolution.

According to sonography instrumentation reference:

“Multiple focal zones improve lateral resolution but at the expense of temporal resolution due to longer acquisition time for each frame.”

Therefore, the correct answer is D: Temporal.

68

Which setting is the most likely cause of the artifact displayed in this image?

A close-up of a ultrasound Description automatically generated

A. Color gain set too low

B. Color gain set too high

C. Velocity scale set too high

D. Velocity scale set too low

Answer: D

Comprehensive and Detailed Explanation From Exact Extract:

The image shows color aliasing, where the colors abruptly change within the vessel indicating wrap-around of Doppler shifts. This happens when the velocity scale (PRF) is set too low, causing velocities exceeding the Nyquist limit to alias.

According to sonography instrumentation reference:

“Aliasing occurs in color Doppler when the flow velocities exceed the Nyquist limit, commonly due to a low velocity scale (PRF).”

Therefore, the correct answer is D: Velocity scale set too low.

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Narrowing the field of view reduces the number of scan lines that need to be processed per frame. This allows the ultrasound system to maintain or even increase the frame rate without compromising temporal resolution. Temporal resolution, which refers to the system's ability to depict motion accurately, is directly related to the frame rate. Reducing the field of view ensures fewer lines are needed to create each image, thus preserving the frame rate and temporal resolution.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments.

Comprehensive and Detailed Explanation From Exact Extract:

The proper care and reprocessing of ultrasound transducers follow a strict hierarchy of steps. The first step is always physical cleaning, which involves removing visible debris, gel, and contaminants from the transducer surface. This must be done prior to any disinfection or sterilization process because organic material can inhibit the effectiveness of these subsequent steps.

According to sonography Principles and Instrumentation documentation:

"Cleaning is the first and essential step in reprocessing ultrasound probes. It removes gel, blood, and other organic material. Disinfection or sterilization should never be performed before cleaning, as residual debris reduces their effectiveness."

Therefore, the correct answer is C: Clean.

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Comprehensive and Detailed Explanation From Exact Extract:

Cross talk (spectral mirror artifact) appears as a duplication of the spectral waveform above and below the baseline. One primary cause is excessive Doppler gain, which amplifies weak signals and noise symmetrically. Reducing gain minimizes this artifact.

Principles and Instrumentation state:

"Cross talk in spectral Doppler may result from high gain settings. Lowering the gain can reduce or eliminate this artifact."

PRF adjustments affect aliasing, not cross talk.

Baseline shifts affect waveform positioning.

Wall filter affects low-frequency signals but not cross talk.

Therefore, the correct answer is A: By decreasing the Doppler gain.

QUESTION NO28

Which artifact is demonstrated by the arrow in this image?

A close-up of an ultrasound Description automatically generated

A. Mirroring

B. Noise

C. Shadowing

D. Enhancement

Answer: C

Comprehensive and Detailed Explanation From Exact Extract:

The image shows an area of signal dropout directly deep to the strongly reflecting structure (likely a vessel wall or calcification), indicated by the arrow. This is a classic example of shadowing artifact.

According to sonography Principles and Instrumentation:

"Shadowing occurs when a highly attenuating or reflective structure blocks the ultrasound beam, resulting in absence of signal distal to the object."

Mirroring (A) produces duplicated structures.

Noise (B) appears as random speckles.

Enhancement (D) produces increased echogenicity distal to an anechoic structure.

Therefore, the correct answer is C: Shadowing.

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Color aliasing in Doppler ultrasound occurs when the velocity of blood flow exceeds the Nyquist limit, causing the color display to wrap around and display high velocities incorrectly as the opposite direction. This phenomenon is characterized by a mix of colors that indicate flow in both directions at the same location. In the provided image, there is a clear presence of color aliasing, as evidenced by the abrupt color change across the vessel, which is not consistent with normal flow patterns.

The Nyquist limit, which is the maximum detectable velocity before aliasing occurs, is directly related to the pulse repetition frequency (PRF). Increasing the color scale on the ultrasound machine effectively increases the PRF. When the PRF is increased, the Nyquist limit is also increased, allowing for the measurement of higher velocities without aliasing.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments. Elsevier.

Contrast agents used in ultrasound imaging typically consist of microbubbles filled with gas. The significant mismatch in acoustic impedance between the gas in the microbubbles and the surrounding blood creates strong reflectors of the ultrasound waves, enhancing the echogenicity of blood and improving the visibility of blood flow and tissue perfusion. The high contrast provided by the gas-filled microbubbles makes them particularly effective as ultrasound contrast agents.

Comprehensive and Detailed Explanation From Exact Extract:

A tissue-mimicking phantom contains small targets at known separations to evaluate the system’s axial resolution, lateral resolution, depth calibration, and more.

Principles and Instrumentation state:

"Tissue-mimicking phantoms assess spatial resolution (axial, lateral), depth accuracy, and penetration performance."

Hydrophones (B) measure acoustic pressure.

Beam profilers (C) assess beam characteristics.

Doppler phantoms (D) test Doppler function.

Therefore, the correct answer is A: Tissue-mimicking phantom.

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The quality factor (Q-factor) is a dimensionless parameter that describes the efficiency of the transducer in terms of bandwidth and operating frequency. It is defined as the ratio of the operating frequency to the bandwidth. A higher Q-factor indicates a narrower bandwidth relative to the operating frequency, resulting in more precise frequency characteristics but potentially reduced axial resolution. Conversely, a lower Q-factor indicates a broader bandwidth, which improves axial resolution but may result in less precise frequency characteristics.

Comprehensive and Detailed Explanation From Exact Extract:

Lateral resolution is the system’s ability to distinguish two structures side-by-side. It is directly determined by the beam width — the narrower the beam, the better the lateral resolution.

Principles and Instrumentation:

"Lateral resolution depends on beam width at a given depth. Narrower beams provide better lateral resolution."

Depth of penetration influences maximum imaging depth.

Propagation speed is largely constant in soft tissue.

Wavelength affects axial resolution.

Therefore, the correct answer is A: Beam width.

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Color flow Doppler imaging displays the mean Doppler frequency shift, which represents the average velocity of blood flow within a sample volume. The ultrasound system uses autocorrelation to process Doppler signals and compute the mean frequency shift. This provides a color-coded map of blood flow velocities, allowing for visualization of flow direction and speed. The mean Doppler frequency is displayed as different colors, with each color representing a range of velocities.

In the given image of a tissue-mimicking phantom, Option B (yellow box) is used to evaluate axial resolution. Axial resolution refers to the ability of the ultrasound system to distinguish between two structures that are close to each other along the path of the ultrasound beam (i.e., parallel to the beam). The targets in Option B are typically aligned in such a way to test the system's capacity to differentiate between structures that are situated closely together along the beam’s axis.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Sonography: Principles and Instruments" by Joan P. Baker and Marveen Craig

Comprehensive and Detailed Explanation From Exact Extract:

Higher frequency transducers provide better axial resolution due to their shorter wavelengths and spatial pulse lengths. This allows finer detail when imaging superficial structures where penetration is not a concern.

According to sonography instrumentation reference:

“Higher frequencies result in shorter pulse lengths, improving axial resolution and making them ideal for superficial imaging.”

Therefore, the correct answer is D: Improved axial resolution.

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Power Doppler, unlike color Doppler, is less angle dependent because it detects the strength of the Doppler signal rather than the velocity of the blood flow. This means it is more sensitive to detecting low-velocity flow and flow in smaller vessels, regardless of the angle between the ultrasound beam and the flow direction. Color Doppler provides information on flow direction and velocity but is highly dependent on the angle of insonation, making it less reliable when the angle is suboptimal.

ARDMS Sonography Principles and Instrumentation guidelines

Zwiebel, W. J., & Pellerito, J. S. (2017).Introduction to Vascular Ultrasonography. Elsevier.

Comprehensive and Detailed Explanation From Exact Extract:

In phased arrays, transmit focus is electronically controlled by varying the timing (delays) of the activation of elements.

Principles and Instrumentation state:

"Electronic focusing is achieved by introducing varying time delays to individual elements, allowing beam focusing at different depths."

Mechanical rotation (A) applies to older mechanical probes.

Matching layers (B) and acoustic lens impedance (C) do not control focusing electronically.

Therefore, the correct answer is D: Adjusting relative delay times of the array elements.

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The calipers shown in the image are used to measure the depth of structures within the ultrasound image. This performance characteristic, known as depth measurement accuracy, assesses how accurately the ultrasound system can measure the distance from the transducer to a specific point within the body. Accurate depth measurements are crucial for diagnostic purposes, ensuring that anatomical and pathological structures are correctly identified and evaluated.

American Registry for Diagnostic Medical Sonography (ARDMS) Sonography Principles and Instrumentation study materials.

Textbook of Diagnostic Sonography by Hagen-Ansert, S. L. (latest edition).

Comprehensive and Detailed Explanation From Exact Extract:

Speckle is a form of acoustic noise caused by interference of scattered echoes. Spatial compounding acquires multiple images from different angles and combines them to reduce speckle, enhance tissue texture, and improve visualization of structures that may otherwise be obscured by attenuation or artifact. The Principles and Instrumentation documentation states:

"Spatial compounding averages frames obtained at varying insonation angles. This reduces speckle artifact, smooths tissue texture, and improves visibility of specular reflectors and deeper structures."

Therefore, the correct answer is D: Spatial compounding.

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The Doppler shift is directly related to the cosine of the angle between the ultrasound beam and the direction of blood flow. As the angle increases from 30 degrees to 60 degrees, the cosine of the angle decreases (cosine of 30 degrees is approximately 0.87, while cosine of 60 degrees is 0.5). Since the Doppler shift is proportional to the cosine of the angle, increasing the angle results in a decreased Doppler shift. This means the measured blood flow velocities will appear lower at a 60-degree angle compared to a 30-degree angle.

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

Comprehensive and Detailed Explanation From Exact Extract:

When color Doppler gain is set too high, the system amplifies noise signals, leading to random color speckles appearing within anechoic or hypoechoic areas where no true flow exists. This artifact is known as "color bleeding" or "color noise."

According to sonography instrumentation reference:

“Excessive color Doppler gain can cause noise to overwrite areas without flow, resulting in false color signals within fluid-filled or hypoechoic structures.”

Therefore, the correct answer is D: Color gain set too high.

62

Which adjustment was made to change image A to produce image B?

A close-up of an ultrasound Description automatically generated

A. Increased overall gain

B. Decreased overall gain

C. Increased dynamic range

D. Decreased dynamic range

Answer: D

Comprehensive and Detailed Explanation From Exact Extract:

In Image B, compared to Image A, you can observe a higher contrast image with darker darks and brighter brights, indicating that dynamic range has been reduced. Decreasing dynamic range results in less grey scale, creating a more black-and-white appearance and emphasizing contrast differences.

According to sonography instrumentation reference:

“Reducing dynamic range increases image contrast by narrowing the range of displayed echo intensities, making the image appear more black and white.”

Therefore, the correct answer is D: Decreased dynamic range.

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Comprehensive and Detailed Explanation From Exact Extract:

The wall filter in Doppler ultrasound is designed to eliminate low-frequency signals, typically associated with motion artifacts such as vessel wall or tissue motion. These low-frequency signals are not part of the desired blood flow signal and can interfere with accurate Doppler display.

When the wall filter setting is increased, it removes these low-frequency signals from the Doppler spectrum. However, increasing the wall filter too much can also eliminate true low-velocity flow information, leading to a loss of clinically relevant data.

This principle is described in official sonography Principles and Instrumentation references:

"Increasing the wall filter will reduce the display of low-frequency Doppler shifts, which are typically associated with slow-moving structures. These low-frequency signals can represent either slow blood flow or tissue motion artifacts."

Therefore, the correct answer isD: Reduced display of low-frequency shifts.

Comprehensive and Detailed Explanation From Exact Extract:

Temporal resolution refers to the system's ability to accurately track moving structures over time (i.e., frame rate). Temporal resolution improves when:

The number of focal zones is reduced (fewer focal zones = faster frame rate).

The imaging depth is reduced (shallower depth = faster frame rate).

According to sonography instrumentation references:

“Fewer focal zones and shallow imaging depth optimize temporal resolution by decreasing the time required for each frame, resulting in a higher frame rate.”

Therefore, the correct answer is C: Fewer focal zones and shallower depth.

55

Which region of this image from a sector phantom is evaluating the dead zone?

A close-up of a ultrasound Description automatically generated

A. Region A

B. Region B

C. Region C

D. Region D

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

The dead zone in ultrasound refers to the shallow area immediately beneath the transducer where no useful data can be collected due to the transducer's ring-down and the time required for the system to switch from transmit to receive mode.

In a sector phantom image, the area closest to the transducer (superficial portion) is used to evaluate the dead zone. In this image, Region A is located at the top of the image, closest to the transducer surface.

According to sonography instrumentation reference:

“The dead zone is assessed by evaluating the area immediately beneath the transducer. This area is used to test the system's near-field performance and transducer surface integrity.”

Therefore, the correct answer is A: Region A.

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Comprehensive and Detailed Explanation From Exact Extract:

Compression reduces the dynamic range of the returning echoes, which alters how many shades of gray are displayed. It compresses the range of signal amplitudes to fit into the grayscale display range.

According to sonography instrumentation reference:

“Compression alters the dynamic range, adjusting how many shades of gray are displayed to optimize image contrast.”

Therefore, the correct answer is B: The shades of gray displayed.

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Temporal resolution refers to the ability of the ultrasound system to distinguish events occurring closely in time. In color flow imaging, temporal resolution is affected by the frame rate, which can be increased by decreasing the width of the color field of view. This is because a narrower color field requires fewer scan lines to be processed, allowing for more frames to be captured per second.

ARDMS Sonography Principles and Instrumentation guidelines

Edelman, S. K. (2017). Understanding Ultrasound Physics.

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.

Reject: This control eliminates low-level noise and weak signals, affecting image quality but not primarily used for contrast resolution.

Output Power: This adjusts the intensity of the transmitted ultrasound waves but does not directly change contrast resolution.

Gain: This control amplifies all signals equally, affecting brightness but not specifically the contrast resolution.

Dynamic Range: Adjusting the dynamic range changes the range of grayscale that the ultrasound system displays, which directly affects the contrast resolution by altering how many shades of gray are visible between the black and white extremes.

Option B demonstrates appropriate spectral Doppler gain. Appropriate gain settings ensure that the Doppler signal is adequately amplified without introducing excessive noise or artifacts. In Option B, the spectral waveform is clearly visible with distinct borders, and the background noise is minimal. In contrast, other options might show either under-gained (too little signal) or over-gained (excessive noise and signal) images, making it difficult to accurately interpret the spectral Doppler information.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Understanding Ultrasound Physics" by Sidney K. Edelman

Lateral resolution refers to the ability to distinguish two structures that are side by side. It is dependent on the width of the ultrasound beam. By decreasing the depth of field, the beam width is reduced at any given point along the depth, which improves the lateral resolution. This is because a narrower beam can better distinguish between objects that are close together laterally.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments.

Acoustic Shadowing: This artifact occurs when a structure absorbs or reflects most of the ultrasound waves, causing a shadow behind the structure. It does not cause improper positioning of a reflector on the display.

Speckle: This is a form of noise in ultrasound imaging that appears as granular texture. It can affect image quality but does not lead to improper positioning of reflectors.

Enhancement: This artifact occurs when the area behind a weakly attenuating structure appears brighter. It affects the brightness of the image but does not affect the position of reflectors.

Range Ambiguity: This occurs when an echo is received after the next pulse has been sent out, causing the reflector to be placed at an incorrect depth on the display. This is because the system assumes the echo came from the most recent pulse.

When a reflector (such as red blood cells) is moving toward the sound source, the frequency of the reflected sound waves increases. This phenomenon is known as the Doppler effect. The frequency shift occurs because the motion of the reflector compresses the sound waves, leading to a higher frequency than the emitted frequency. This increased frequency is what the Doppler ultrasound system detects and uses to calculate the velocity of the moving reflector.

ARDMS Sonography Principles and Instrumentation guidelines

Hoskins, P. R., Thrush, A., Martin, K., & Whittingham, T. A. (2010). Diagnostic Ultrasound: Physics and Equipment.

Spectral Doppler mirroring, also known as crosstalk, occurs when the Doppler signal appears on both sides of the baseline. This can be caused by excessively high Doppler gain, which amplifies the signal and creates artificial mirror images. Decreasing the Doppler gain reduces the signal amplitude, thereby minimizing the mirroring artifact.

ARDMS Sonography Principles and Instrumentation guidelines

Hoskins, P. R., Thrush, A., Martin, K., & Whittingham, T. A. (2010). Diagnostic Ultrasound: Physics and Equipment.

Lateral resolution refers to the ability of the ultrasound system to distinguish two structures that are side by side, perpendicular to the direction of the sound beam. This resolution is primarily improved by reducing the beamwidth. A narrower beamwidth allows for better differentiation between adjacent structures, enhancing the lateral resolution. Higher frequency transducers can also help achieve a narrower beamwidth, but beamwidth is the primary factor.

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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Compression in ultrasound imaging adjusts the range of grayscale displayed, affecting the contrast resolution.

This function allows sonographers to enhance the differentiation between structures of varying echogenicities.

By modifying the contrast resolution, sonographers can better visualize subtle differences in tissue composition and improve the diagnostic quality of the images.

Increasing contrast resolution is particularly important in differentiating between fluid-filled cysts and solid masses.References:

ARDMS Sonography Principles and Instrumentation guidelines on image processing and contrast resolution.

When utilizing multiple transmit focal zones, the ultrasound system must perform multiple transmissions at each focal depth. This process requires more time for data acquisition, which in turn decreases the frame rate. A lower frame rate directly impacts temporal resolution, which is the ability to accurately depict moving structures over time. Thus, using multiple focal zones improves lateral resolution but degrades temporal resolution.

Comprehensive and Detailed Explanation From Exact Extract:

Spectral Doppler aliasing occurs when the Doppler frequency shift exceeds the Nyquist limit. The Doppler shift is proportional to the cosine of the Doppler angle. Increasing the Doppler angle (moving closer to 90 degrees) reduces the cosine value, thus reducing the Doppler shift frequency and helping to avoid aliasing.

According to sonography instrumentation reference:

“Increasing the Doppler angle reduces the Doppler shift frequency, thus decreasing the likelihood of aliasing in spectral Doppler.”

Therefore, the correct answer is A: Increase Doppler angle.

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Comprehensive and Detailed Explanation From Exact Extract:

M-mode (motion mode) ultrasound records the movement of structures along a single scan line over time. It is particularly valuable in cardiac imaging where precise motion of heart valves and walls is evaluated.

Principles and Instrumentation reference:

"M-mode is primarily used in echocardiography to evaluate the motion of cardiac structures with high temporal resolution."

Liver, kidneys, and pancreas are evaluated using B-mode, not M-mode.

Therefore, the correct answer is A: Heart.

QUESTION NO20

Which color control adjustment caused the change from image A to image B?

A close-up of a medical image Description automatically generated

A. Map

B. Velocity scale

C. Wall filter

D. Color packet size

Answer: B

Comprehensive and Detailed Explanation From Exact Extract:

In image A, the vessel shows uniform color filling without aliasing. In image B, multiple color bands are present, indicating color aliasing — where the flow velocities exceeded the Nyquist limit due to a lower velocity scale (PRF).

According to sonography Principles and Instrumentation:

"Aliasing in color Doppler appears when the Doppler shift exceeds the Nyquist limit. Reducing the velocity scale increases the likelihood of aliasing."

Changing the map (A) would modify the color hues but not introduce aliasing.

Wall filter (C) affects low-velocity signals but not aliasing.

Color packet size (D) affects frame rate and sensitivity, not aliasing directly.

Therefore, the correct answer is B: Velocity scale.

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