Free ARDMS SPI Practice Exam with Questions & Answers | Set: 5

Axial resolution refers to the ability to distinguish two structures that are close to each other along the path of the ultrasound beam.

Spatial pulse length (SPL) is the distance over which one pulse occurs, and it directly affects axial resolution.

Shorter SPL improves axial resolution because it allows better differentiation of closely spaced structures.

The axial resolution is improved by increasing the frequency of the transducer, which shortens the wavelength and hence the SPL.References:

ARDMS Sonography Principles and Instrumentation guidelines on resolution parameters and their impact on image quality.

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.

Comprehensive and Detailed Explanation From Exact Extract:

Wavelength is inversely proportional to frequency according to the equation:

Wavelength (λ) = Propagation speed (c) / Frequency (f)

If frequency decreases from 10 MHz to 5 MHz, the wavelength increases by a factor of 2 (doubles).

Principles and Instrumentation state:

"As frequency decreases, wavelength increases. Halving the frequency results in doubling the wavelength."

Therefore, the correct answer is D: Doubles.

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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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Attenuation in ultrasound is directly proportional to the path length. If the path length is doubled, the amount of attenuation is also doubled. Attenuation refers to the reduction in the amplitude and intensity of the ultrasound wave as it travels through tissue, primarily due to absorption, reflection, and scattering. The relationship is linear, so doubling the distance the sound wave travels will result in twice the amount of attenuation.

ARDMS Sonography Principles and Instrumentation guidelines

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

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.

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).

Write magnification, or pre-processing zoom, involves rescanning the region of interest (ROI) with more scan lines, thus acquiring new data for that specific area. This process increases the spatial resolution of the image in the magnified area because it gathers more detailed data by adjusting the scan parameters, resulting in improved image quality. This is different from read magnification (post-processing zoom), which simply enlarges the existing image data without increasing resolution.

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:

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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