The imaging depth selected by the sonographer affects which parameter?

• A. Pulse repetition period
• B. Pulse duration
• C. Wavelength
• D. Acoustic impedance

Answer: (A)

Imaging depth sets the time window for echoes—the round‑trip travel time the system must wait before the next pulse. This is the pulse repetition period. The deeper you image, the longer it takes for sound to travel there and back, so PRP increases (PRP ≈ 2 × depth / speed of sound in tissue, about 1540 m/s). Because the frame rate is the reciprocal of PRP, deeper imaging also lowers the pulse repetition frequency. Pulse duration, the length of each emitted pulse, is determined by the transducer itself and remains the same regardless of depth. Wavelength, set by the sound speed and the transmitted frequency, also doesn’t change with depth. Acoustic impedance depends on tissue properties and is not altered by how deep you image. So the imaging depth you choose directly affects the pulse repetition period.