How is reflector depth determined in pulse-echo ultrasound?

How is reflector depth determined in pulse-echo ultrasound?

• A. Echo amplitude
• B. Echo arrival time
• C. Echo frequency
• D. Echo phase

Answer: (B)

Reflector depth is found from the time it takes for a pulse to travel to a boundary and back as an echo. The system measures the echo arrival time (time-of-flight) after transmission. Because the sound must make a round trip, depth is half the product of the travel time and the speed of sound in tissue: depth ≈ (c × t)/2. In soft tissue, c is about 1540 m/s, though the system uses a fixed value for calculations. This timing is what converts distance into the image; echo amplitude, frequency, or phase relate to reflectivity, frequency content, or motion, not the depth measurement.

Reflector depth is found from the time it takes for a pulse to travel to a boundary and back as an echo. The system measures the echo arrival time (time-of-flight) after transmission. Because the sound must make a round trip, depth is half the product of the travel time and the speed of sound in tissue: depth ≈ (c × t)/2. In soft tissue, c is about 1540 m/s, though the system uses a fixed value for calculations. This timing is what converts distance into the image; echo amplitude, frequency, or phase relate to reflectivity, frequency content, or motion, not the depth measurement.