SPI Questions and Answers

Attenuation refers to the reduction in the intensity of the ultrasound beam as it travels through tissue. Higher frequency ultrasound beams experience more attenuation because they are absorbed and scattered more than lower frequency beams. This is due to the fact that higher frequency waves have shorter wavelengths and interact more with the small particles in tissues, causing greater energy loss.

Comprehensive and Detailed Explanation From Exact Extract:

Axial resolution is primarily determined by the spatial pulse length (SPL), which depends on both wavelength and the number of cycles per pulse. A shorter pulse length provides better axial resolution. The Principles and Instrumentation documents state:

"Axial resolution = SPL/2. To improve axial resolution, the pulse duration must be shortened — achieved by decreasing the pulse length."

Note: While increasing frequency also improves axial resolution (because it shortens wavelength), in this question, decreasing pulse length directly targets SPL, making it the most precise answer.

Therefore, the correct answer is C: Pulse length.

QUESTION NO6

In this image, which artifact is demonstrated?

A close-up of a sound wave Description automatically generated

A. Mirroring

B. Aliasing

C. Range ambiguity

D. Spectral broadening

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

The provided image shows a pulsed-wave Doppler spectral display. There are two identical Doppler spectra present — one on the top and an inverted one on the bottom — a classic appearance of the mirroring artifact.

Mirroring occurs when the strong Doppler signal reflects off a highly reflective interface and produces a duplicate signal on the opposite side of the baseline. The mirrored signal mimics the original spectral waveform but appears as a reversed, symmetric version.

According to official sonography Principles and Instrumentation references:

"Mirror image artifact in Doppler (also called cross-talk) occurs when a strong signal is incorrectly displayed on both sides of the baseline, producing a duplicated waveform."

Aliasing would show wrap-around of velocities beyond the Nyquist limit, typically producing a cutoff and color reversal — not seen here.

Range ambiguity produces overlapping signals from different depths — also not applicable here.

Spectral broadening would result in widening of the Doppler spectral trace — which is not evident here.

Therefore, the correct answer is A: Mirroring.

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Noise in the Doppler waveform can often be attributed to excessive gain settings. Decreasing the Doppler gain reduces the amplification of both the signal and the noise, thus providing a clearer and more accurate Doppler waveform. Excessive gain can cause speckling and clutter, which obscure the true Doppler signals. By reducing the gain, the noise level is minimized, resulting in a cleaner Doppler signal representation.

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.

Comprehensive and Detailed Explanation From Exact Extract:

Mechanical Index (MI) is proportional to the peak negative pressure and inversely proportional to the square root of frequency. Lowering output power directly decreases the peak pressure, thus reducing MI.

Principles and Instrumentation state:

"Mechanical index decreases with lower output power, reducing the risk of mechanical bioeffects such as cavitation."

Lowering frequency (A) increases MI.

Tissue harmonics (B) improves image quality but does not reduce MI directly.

Increasing gain (D) affects displayed brightness, not acoustic power.

Therefore, the correct answer is C: Decreasing output power.

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Comprehensive and Detailed Explanation From Exact Extract:

Mechanical Index (MI) estimates the likelihood of non-thermal bioeffects such as cavitation (formation of microbubbles).

Principles and Instrumentation state:

"Mechanical Index reflects the risk of cavitation. Higher MI values increase cavitation potential."

Attenuation coefficient (A) refers to energy loss.

Thermal index (C) reflects potential heating.

Frame rate (D) relates to temporal resolution.

Therefore, the correct answer is B: Mechanical index.

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QUESTION NO42

Which target group is used to evaluate transverse distance measurement accuracy in this tissue-mimicking phantom image?

A ultrasound image of a baby Description automatically generated with medium confidence

A. A

B. B

C. C

D. D

Answer: C

Comprehensive and Detailed Explanation From Exact Extract:

In a tissue-mimicking phantom, the group of targets aligned side-by-side (horizontally) is used to evaluate transverse (lateral) distance measurement accuracy. In the image, target group C (in red) represents the lateral spacing targets.

Principles and Instrumentation state:

"Transverse distance accuracy is evaluated using laterally spaced targets in the phantom to verify correct lateral measurement calibration."

Group A (top) is typically for near field assessment.

Group B may be for axial resolution or cyst evaluation.

Group D (deep) may assess depth calibration or sensitivity.

Therefore, the correct answer is C: C.

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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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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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The artifact demonstrated in the image is mirroring. This occurs when the ultrasound beam encounters a strong reflector, such as a diaphragm or pleura, and is reflected back and forth between the object and the transducer. This results in a duplicate image appearing on the other side of the strong reflector, creating a mirror image artifact. It is crucial for sonographers to recognize and differentiate this artifact from actual anatomical structures to avoid misinterpretation.

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

Diagnostic Ultrasound: Principles and Instruments by Kremkau, F. W. (latest edition).

Comprehensive and Detailed Explanation From Exact Extract:

Slice thickness (elevational resolution artifact) occurs when the ultrasound beam partially includes surrounding tissue above or below the scan plane, falsely appearing as internal echoes within an otherwise anechoic cyst.

Principles and Instrumentation:

"Slice thickness artifact occurs when off-axis echoes are included in the imaging slice, falsely creating internal echoes in cystic structures."

Refraction (A) causes displacement.

Enhancement (B) causes posterior brightening.

Range ambiguity (D) produces incorrect depth placement.

Therefore, the correct answer is C: Slice thickness.

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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.

The frame rate in color flow imaging is influenced by several factors, one of the most significant being line density. Line density refers to the number of ultrasound lines used to create an image. Increasing line density improves spatial resolution but requires more time to acquire each frame, thereby reducing the frame rate. Other factors such as filter selection, dynamic range, and variance map selection can affect the quality of the color flow image, but they do not have as direct an impact on frame rate as line density does.

Comprehensive and Detailed Explanation From Exact Extract:

Harmonic imaging operates by transmitting at the fundamental frequency and receiving echoes at the second harmonic frequency (which is twice the fundamental frequency). Therefore, the transducer must have a broad enough bandwidth to include both frequencies.

According to sonography instrumentation reference:

“For harmonic imaging, the transducer bandwidth must accommodate both the transmitted fundamental frequency and the received second harmonic frequency.”

Therefore, the correct answer is A: Fundamental and second harmonic frequencies.

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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.

The propagation speed of sound in a medium is determined by the medium's elasticity and density. Elasticity refers to the ability of the medium to return to its original shape after deformation, while density is the mass per unit volume of the medium. The speed of sound increases with higher elasticity and decreases with higher density. This relationship is described by the equation????=????????v=ρE​​, where????vis the propagation speed,????Eis the elasticity (or modulus of elasticity), and????ρis the density.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

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

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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Comprehensive and Detailed Explanation From Exact Extract:

Reducing transducer frequency lowers the Doppler shift for a given velocity (since Doppler shift is directly proportional to frequency), which helps avoid aliasing when high velocities are present.

According to sonography instrumentation reference:

“Lowering the transducer frequency decreases Doppler shift, reducing the likelihood of aliasing.”

Therefore, the correct answer is C: Decrease transducer frequency.

91

Which direction is blood flowing in this image?

A close-up of a ultrasound Description automatically generated

A. Right to left

B. Left to right

C. Bidirectional

D. Indeterminate

Answer: B

Comprehensive and Detailed Explanation From Exact Extract:

In the color Doppler image, the color bar indicates that red represents flow toward the transducer and blue represents flow away from the transducer. The vessel displays red flow on the left side and blue on the right side, indicating flow direction from left to right across the image.

According to sonography instrumentation reference:

“Color Doppler maps flow direction according to the color scale. Flow toward the transducer is coded as red, and away is coded as blue.”

Therefore, the correct answer is B: Left to right.

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All answers are fully verified, 100% accurate, and aligned with Sonography Principles and Instrumentation documentation.

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A string phantom is designed to evaluate the accuracy of Doppler ultrasound systems, specifically in measuring flow velocity. It consists of a moving string or filament that mimics blood flow within a vessel. By using this phantom, sonographers can assess how accurately the ultrasound system can detect and measure the speed of the moving target. This helps in calibrating and verifying the performance of Doppler systems, ensuring they provide accurate flow velocity readings in clinical practice.

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:

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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Time Gain Compensation (TGC), also known as Depth Gain Compensation (DGC), is used to adjust the amplification of ultrasound signals based on their depth. As ultrasound waves travel deeper into the tissue, they become weaker due to attenuation. TGC compensates for this attenuation by progressively increasing the gain for deeper echoes, ensuring that structures at different depths appear with similar brightness on the ultrasound image. This function is critical for creating a uniform image and accurately visualizing deeper anatomical structures.

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

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:

Each additional focal zone requires extra transmissions per scan line, which slows down frame acquisition, thereby reducing the frame rate.

Principles and Instrumentation state:

"Increasing the number of focal zones lowers frame rate because multiple pulses are needed per scan line for each focal depth."

Increasing PRF (B) allows faster data acquisition.

Decreasing depth (C) shortens round-trip time, increasing frame rate.

Decreasing sector width (D) reduces scan lines, increasing frame rate.

A wall filter in Doppler ultrasound is designed to remove low-frequency signals that are often caused by tissue motion, vessel wall movement, or other forms of motion artifact. These low-frequency signals can clutter the Doppler spectrum, making it difficult to accurately interpret blood flow velocities. By filtering out these unwanted low-frequency signals, the wall filter helps to enhance the clarity of the Doppler signal, allowing for more accurate measurements of blood flow velocities.

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

Gray-scale evaluation in a tissue-mimicking phantom involves assessing the uniformity and accuracy of the gray-scale representation of the tissues.

Option C typically contains structures designed to test the machine's ability to accurately depict varying levels of echogenicity, which is essential for proper gray-scale evaluation.

This area will have a range of echo intensities that help in determining the contrast resolution and the ability of the system to distinguish between different tissue types based on their gray-scale values.References:

ARDMS Sonography Principles and Instrumentation guidelines on tissue-mimicking phantoms and image quality evaluation.

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.

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:

Overall gain amplifies the strength of all returning echoes equally, regardless of depth. It does not affect the transmitted pulse or selectively compensate for attenuation; it simply amplifies received signals uniformly.

According to sonography instrumentation reference:

“Overall gain controls the amplification of all returning echoes across the entire image, increasing brightness uniformly at all depths.”

Therefore, the correct answer is B: Amplification of signals from all depths.

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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:

Reflection is maximized when the ultrasound beam strikes a tissue interface at 90 degrees (perpendicular). This angle provides optimal return of echoes for imaging.

According to sonography instrumentation reference:

“Maximal reflection occurs when the sound beam strikes a boundary at 90 degrees.”

Therefore, the correct answer is D: Reflection.

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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.

Low persistence is best used for visualizing dynamic structures. Persistence is a setting that controls the averaging of successive frames to reduce noise and improve image quality. While high persistence can be beneficial for imaging static structures by providing a smoother image, it can blur or smear moving structures, making it difficult to visualize motion accurately. Low persistence settings allow for better temporal resolution and are therefore ideal for observing dynamic or moving structures such as the heart or blood flow.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

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

Comprehensive and Detailed Explanation From Exact Extract:

Axial resolution depends on spatial pulse length (SPL), which is determined by the number of cycles per pulse. Fewer cycles per pulse shorten the SPL, thereby improving axial resolution and allowing better separation of closely spaced structures along the beam axis.

According to sonography instrumentation reference:

“Axial resolution improves with fewer cycles per pulse, which decreases the spatial pulse length and allows better discrimination of structures along the beam path.”

Therefore, the correct answer is B: Reducing the number of cycles per pulse.

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Transducer beam divergence is influenced by the aperture size and frequency. A smaller aperture and lower frequency result in greater beam divergence. Among the given options, the transducer with a 4 mm aperture and 4 MHz frequency will have the greatest divergence. This is because the smaller aperture size contributes to a wider beam spread, and the lower frequency also increases the divergence compared to higher frequencies.

ARDMS Sonography Principles and Instrumentation guidelines

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

Comprehensive and Detailed Explanation From Exact Extract:

The imaging depth is limited by the frequency of the transducer because higher frequency sound waves attenuate more rapidly as they penetrate tissue, reducing maximum depth capability.

According to Principles and Instrumentation:

"Higher frequencies provide better resolution but have increased attenuation, limiting penetration depth. Lower frequencies penetrate deeper but at the cost of resolution."

Propagation speed is relatively constant in soft tissue (~1540 m/s), amplitude affects signal strength but not depth limit directly, and focal depth is an adjustable beam parameter.

Therefore, the correct answer is B: Frequency.

QUESTION NO15

Which color Doppler setting adjustment would likely demonstrate color flow in the normal vein seen in this image?

An ultrasound image of veins and veins Description automatically generated

A. Decreasing scale

B. Increasing scale

C. Decreasing persistence

D. Increasing persistence

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

Veins generally exhibit low-velocity flow. The color scale (or velocity range) must be low enough to detect these slow flows. Decreasing the scale lowers the Nyquist limit, allowing the machine to display lower velocities that may otherwise be undetectable.

Principles and Instrumentation state:

"Reducing the scale increases sensitivity to low-velocity flows such as venous flow, while high scales may suppress these signals."

Therefore, the correct answer is A: Decreasing scale.

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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In the provided image, data below the baseline represents blood flow moving away from the transducer, which can indicate retrograde flow. When using spectral Doppler, the baseline separates flows towards and away from the transducer. Aliasing occurs when the velocity of blood flow exceeds the Nyquist limit, causing the display to wrap around and appear on the opposite side of the baseline. This phenomenon is common in high-velocity flow situations and results in part of the flow being displayed below the baseline. Retrograde flow further supports this, as it shows blood moving in the opposite direction to the expected flow.

The settings that lead to the highest temporal resolution are those that reduce the amount of information that the ultrasound system needs to process, allowing for a higher frame rate. A smaller sector width and shallower scan depth reduce the area that needs to be imaged, enabling faster data acquisition. Turning off color Doppler further reduces processing demands, as the system no longer needs to compute and display color flow information. Therefore, a 45-degree sector width, 4 cm scan depth, and color Doppler off will provide the highest temporal resolution.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

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

Lateral resolution describes the ability of an ultrasound system to distinguish between two structures that are side by side (perpendicular to the path of the ultrasound beam). This type of resolution depends on the beam width; narrower beams provide better lateral resolution. As the ultrasound beam travels deeper into the tissue, it generally widens, which can reduce lateral resolution. Techniques such as focusing the beam can help improve lateral resolution at specific depths by narrowing the beam width.

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

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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Comprehensive and Detailed Explanation From Exact Extract:

Power Doppler detects the strength (amplitude) of returning Doppler signals, which reflects the presence of flow regardless of direction or velocity. It is more sensitive to low-velocity flow and is less angle-dependent than conventional color Doppler.

Principles and Instrumentation state:

"Power Doppler displays the amplitude of Doppler shifts, representing the presence of flow. It does not display direction or velocity."

Laminar flow (A) and velocity (C) are not specifically measured by power Doppler.

Viscosity (D) cannot be assessed by Doppler ultrasound.

Therefore, the correct answer is B: Presence of flow.

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Axial resolution refers to the ability to distinguish two structures that are close to each other along the direction of the sound beam. It is determined by the spatial pulse length (SPL), which is the product of the number of cycles in a pulse and the wavelength. Shorter SPL means shorter pulse duration, which leads to better axial resolution. This is because shorter pulses allow for better separation of echoes from closely spaced structures.

ARDMS Sonography Principles and Instrumentation guidelines

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

Dynamic range in ultrasound imaging refers to the range of signal amplitudes that the system can display. Increasing the dynamic range allows the ultrasound system to display a broader range of echo amplitudes, which enhances the contrast resolution and helps to visualize subtle differences in tissue texture and borders of anatomical structures. When the dynamic range is increased, more shades of gray are used, making the image appear softer and less contrasty, which is beneficial for delineating the borders of anatomical structures more clearly.

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

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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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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Comprehensive and Detailed Explanation From Exact Extract:

When color "bleeds" outside vessel walls, it often results from motion artifacts or noise from slow tissue motion being displayed as flow. Increasing the wall filter eliminates low-frequency Doppler shifts caused by motion, improving color accuracy within vessel boundaries.

According to sonography instrumentation reference:

“Raising the wall filter eliminates low-velocity signals from vessel wall motion, reducing the appearance of color outside the vessel lumen.”

Therefore, the correct answer is C: Increasing wall filter.

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Overall gain controls the amplification of all the received ultrasound signals uniformly. This adjustment affects the brightness of the entire image by increasing or decreasing the amplification of the echoes returning from all depths. It is a primary control for adjusting image brightness. The overall gain should be set to an appropriate level to ensure that the ultrasound image is neither too bright (over-gained) nor too dark (under-gained), allowing for optimal visualization of the anatomical structures.

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

Comprehensive and Detailed Explanation From Exact Extract:

Interpolation estimates pixel values between scan lines by averaging adjacent data, filling in gaps to create a smoother, more complete image without additional scanning.

According to sonography instrumentation reference:

“Interpolation is a post-processing technique that fills gaps between scan lines by estimating values based on surrounding echoes, improving image smoothness.”

Therefore, the correct answer is D: Interpolation.

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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.

The waveform in the image shows spectral Doppler signals that are pushed against the upper limit of the display, indicating that the baseline is too high. Lowering the baseline allows for a better visual representation of the entire Doppler signal within the available display range. This adjustment prevents the waveform from being cut off and helps in accurately interpreting the blood flow characteristics.

Range ambiguity artifact occurs when echoes from one pulse are received after the next pulse has been emitted, leading to the incorrect placement of echoes at shallower depths than their true location. This artifact typically happens when the PRF is set too high, causing the ultrasound system to interpret delayed echoes as coming from the current pulse rather than the previous one. This results in reflectors appearing closer to the transducer than they actually are.

The maximum Doppler shift that can be detected without aliasing is determined by the Nyquist limit, which is half of the pulse repetition frequency (PRF). If the PRF is 3 kHz, the Nyquist limit is3????????????2=1.5????????????23kHz​=1.5kHz. Therefore, the maximum Doppler shift that can be detected without aliasing is 1.5 kHz. Aliasing occurs when the Doppler shift exceeds this limit, causing an incorrect representation of the velocity.