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ARDMS SPI Exam
Sonography Principles and Instrumentation (Page 7 )

Updated On: 7-Feb-2026
Page 7 of 44
PDF with 215 Questions

What is effected by increasing the color scale?

  1. The Nyquist limit is increased
  2. More colors are displayed
  3. The color box width decreases
  4. The color priority decreases

Answer(s): A

Explanation:

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.


Reference:

ARDMS Sonography Principles and Instrumentation guidelines

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



Which change can be made in order to avoid exceeding the Nyquist limit?

  1. Increase output power
  2. Decrease output power
  3. Increase pulse repetition frequency
  4. Decrease pulse repetition frequency

Answer(s): C

Explanation:

To avoid exceeding the Nyquist limit and prevent aliasing in Doppler ultrasound, the pulse repetition frequency (PRF) should be increased. The Nyquist limit is half of the PRF, so by increasing the PRF, the Nyquist limit is raised, allowing the system to accurately measure higher velocities without encountering aliasing artifacts.


Reference:

ARDMS Sonography Principles and Instrumentation guidelines

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



What determines the resonant frequency of a pulsed wave transducer?

  1. Element thickness and pulse repetition frequency
  2. Element diameter and speed of sound in element
  3. Element diameter and element thickness
  4. Element thickness and speed of sound in element

Answer(s): D

Explanation:

The resonant frequency of a pulsed wave transducer is determined by the thickness of the piezoelectric element and the speed of sound within that element. The resonant frequency is inversely proportional to the element thickness and directly proportional to the speed of sound in the material. Thinner elements and higher sound speeds result in higher resonant frequencies, while thicker elements and lower sound speeds result in lower resonant frequencies.


Reference:

ARDMS Sonography Principles and Instrumentation guidelines

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



Which factor does a string phantom evaluate?

  1. Two-dimensional resolution
  2. Intensity values
  3. Flow velocity
  4. Slice thickness

Answer(s): C

Explanation:

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.


Reference:

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

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



Which resolution is improved by focusing?

  1. Lateral
  2. Axial
  3. Temporal
  4. Contrast

Answer(s): A

Explanation:

Focusing improves lateral resolution in ultrasound imaging. Lateral resolution refers to the system's ability to distinguish between two points that are side by side (perpendicular to the sound beam's path). By focusing the ultrasound beam, the width of the beam is narrowed at the focal point, enhancing the system's ability to resolve structures that are close together in the lateral plane. This results in clearer, more detailed images of the anatomical structures.


Reference:

American Registry for Diagnostic Medical Sonography (ARDMS) Sonography Principles and

Instrumentation study materials.

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



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