SPI Exam Dumps - ARDMS SPI Questions and Answers

Ensemble length, also known as packet size or Doppler packet, refers to the number of pulses used to calculate each Doppler measurement. Increasing the number of pulses in an ensemble length improves the accuracy of velocity measurements by providing more data points for the Doppler shift analysis. This leads to better estimation of mean velocities and reduces the variability of the measurements, although it may slightly decrease temporal resolution due to the longer time required to acquire the data.

ARDMS Sonography Principles and Instrumentation guidelines

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

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.

—

Comprehensive and Detailed Explanation From Exact Extract:

Transmit focus narrows the ultrasound beam width at specific depths, improving lateral resolution — the ability to distinguish two objects side-by-side.

According to Principles and Instrumentation:

"Lateral resolution depends on beam width and is improved by focusing, which narrows the beam in the lateral dimension."

Axial resolution depends on pulse length.

Elevational resolution depends on slice thickness.

Temporal resolution relates to frame rate.

Therefore, the correct answer is C: Lateral.

QUESTION NO17

Which statement characterizes the primary difference between image A and image B?

A close-up of a medical scan Description automatically generated

A. Image A demonstrates a better axial resolution.

B. Image A demonstrates a lower overall gain setting.

C. Image A demonstrates a shallower field of view.

D. Image A demonstrates a wider scale of contrast.

Answer: B

Comprehensive and Detailed Explanation From Exact Extract:

In image A, the structures appear darker with less overall brightness compared to image B. This indicates that the overall gain (receiver amplification) is set lower in image A, resulting in a dimmer image. Gain controls how much the returning echoes are amplified after detection.

According to Principles and Instrumentation:

"Overall gain amplifies all returning echoes equally. A lower gain setting results in a darker image, while higher gain brightens the display."

Axial resolution (A) is primarily dependent on frequency and pulse length, not visible here.

Field of view (C) appears similar between both images.

Contrast scale (D) refers to dynamic range, not directly indicated here.

Therefore, the correct answer is B: Image A demonstrates a lower overall gain setting.

—

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.

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

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.