ARDMS Ultrasound Physics & Instrumentation Practice Exam 2026 - Free Ultrasound Practice Questions and Study Guide

The Nyquist limit in Doppler ultrasound is defined by the maximum frequency shift that can be accurately measured. This concept arises from the principles of signal processing and relates to how Doppler ultrasound works. When sound waves are reflected off moving structures, such as blood cells, they undergo a frequency shift that is proportional to the velocity of the moving target.

The Nyquist limit is crucial because it establishes the maximum frequency shift that can be processed without ambiguity, allowing for accurate determination of blood flow velocities. If the frequency shift exceeds the Nyquist limit, the resulting Doppler signal will become "aliased," meaning that higher velocities are incorrectly represented as lower frequencies, leading to incorrect measurements of flow. Therefore, understanding and adhering to the Nyquist limit helps ensure accurate Doppler measurements and interpretations.

Other potential options, while related to ultrasound and its functions, do not capture the essence of the Nyquist limit specifically and its role in frequency measurement.