ARDMS Practice Test 2025 – Comprehensive All-in-One Guide to Diagnostic Medical Sonography Success!

The correct answer focuses on the pulse repetition frequency (PRF). When the imaging depth is increased, the ultrasound machine must adjust certain parameters to avoid range ambiguity, which occurs when the machine cannot determine which pulse corresponds to which echo.

As the imaging depth increases, the time it takes for the sound pulse to travel to the target and return also increases. To accommodate this longer time frame and eliminate the confusion of echoes arriving from different depths (range ambiguity), the pulse repetition frequency needs to be decreased. A lower PRF means that fewer pulses are sent out per second, allowing enough time for the echoes from deeper structures to return before the next pulse is emitted.

By decreasing the PRF, the ultrasound system ensures that each sound pulse has sufficient time to travel to the desired depth and return without overlapping with the subsequent pulse, preventing any misinterpretation of the depth at which the echoes originate.