SPI Online Practice Questions

Explanation:
Comprehensive and Detailed Explanation From Exact Extract:
In pulsed-wave transducers, the thickness of the piezoelectric element primarily determines the fundamental operating frequency. Thinner elements produce higher frequencies, while thicker elements produce lower frequencies.
According to sonography instrumentation reference:
“The operating frequency of a pulsed-wave transducer is primarily determined by the thickness of the piezoelectric crystal. Thinner crystals vibrate at higher frequencies.”
Therefore, the correct answer is A: Element thickness.

Explanation:
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.
Reference
ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide
"Quality Assurance for Ultrasound Imaging Systems" by AAPM (American Association of Physicists in Medicine)

Explanation:
Aliasing in pulsed-wave Doppler occurs when the sampled Doppler frequency exceeds the Nyquist limit, which is half of the pulse repetition frequency (PRF). This results in an incorrect representation of the blood flow velocities, causing the waveform to wrap around and appear on the opposite side of the baseline. To correct aliasing, the PRF should be increased, which raises the Nyquist limit and allows for accurate measurement of higher velocities without aliasing. Increasing the PRF effectively reduces the likelihood of aliasing artifacts in the Doppler signal.
Reference: American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.

Explanation:
M-mode (Motion mode) is used in ultrasound to measure and display the movement of structures over time.
This mode is particularly useful in cardiac imaging to assess the motion of heart walls and valves.
M-mode provides a one-dimensional view of the motion of tissues and is often used in conjunction with 2D imaging for a comprehensive assessment.
It is essential in evaluating the dynamic function of organs, especially in cardiology, where precise measurements of cardiac structures' movement are crucial.
Reference: ARDMS Sonography Principles and Instrumentation guidelines on modes of ultrasound imaging and their clinical applications.

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.