When a reflector is located superficially, the time from pulse creation to reception is ______.

When a reflector is located superficially, the time from pulse creation to reception is ______.

• A. Longer
• B. Directly related
• C. Twice as long
• D. Short

Answer: (D)

The time from pulse creation to echo reception is governed by the two-way travel time of the ultrasound pulse. It is proportional to the depth of the reflector, since the pulse has to travel to the reflector and back. When the reflector lies close to the transducer (superficial), the distance is small, so the two-way travel time is short. Using the approximate speed of sound in soft tissue (about 1540 m/s), the time is t = 2d / c, which yields a very small value for small depths. Therefore, the correct description is that the time is short.

The time from pulse creation to echo reception is governed by the two-way travel time of the ultrasound pulse. It is proportional to the depth of the reflector, since the pulse has to travel to the reflector and back. When the reflector lies close to the transducer (superficial), the distance is small, so the two-way travel time is short. Using the approximate speed of sound in soft tissue (about 1540 m/s), the time is t = 2d / c, which yields a very small value for small depths. Therefore, the correct description is that the time is short.