Pulse repetition frequency is changed by adjusting the:

Pulse repetition frequency (PRF) is influenced by the depth setting of the ultrasound system. PRF is defined as the number of pulses emitted by the transducer per second and is directly related to the maximum imaging depth. When the imaging depth is increased, the time required for the ultrasound pulses to travel to the deeper structures and return to the transducer also increases. Consequently, the system must reduce the PRF to avoid overlapping pulses, which can lead to a phenomenon called range ambiguity.

By adjusting the depth, the sonographer effectively alters how quickly the system can send and receive pulses, allowing for clearer and more accurate imaging of structures at various depths. In summary, increasing depth lowers the PRF, while decreasing depth raises the PRF, enabling optimized imaging based on the target anatomy's location.