What system function is limited by the speed of sound in tissue?

What system function is limited by the speed of sound in tissue?

• A. Demodulation
• B. Pulse repetition frequency
• C. Voltage amplitude
• D. Rectification

Answer: (B)

The speed of sound in tissue limits how quickly the system can emit successive ultrasound pulses because you must wait for the echoes to return from the deepest point you’re imaging before sending the next pulse. That waiting time sets the maximum pulse repetition frequency (PRF). If you fire too many pulses per second, echoes from deeper regions can overlap with the next pulse, causing range ambiguity and depth misassignment. In practice, the maximum PRF is about c/(2dmax), where c is the speed of sound in tissue (roughly 1540 m/s) and dmax is the maximum imaging depth. The other functions—demodulation, voltage amplitude, and rectification—are electrical/signal-processing aspects and aren’t directly constrained by how fast sound travels through tissue.

The speed of sound in tissue limits how quickly the system can emit successive ultrasound pulses because you must wait for the echoes to return from the deepest point you’re imaging before sending the next pulse. That waiting time sets the maximum pulse repetition frequency (PRF). If you fire too many pulses per second, echoes from deeper regions can overlap with the next pulse, causing range ambiguity and depth misassignment. In practice, the maximum PRF is about c/(2dmax), where c is the speed of sound in tissue (roughly 1540 m/s) and dmax is the maximum imaging depth. The other functions—demodulation, voltage amplitude, and rectification—are electrical/signal-processing aspects and aren’t directly constrained by how fast sound travels through tissue.