True or False: A pulsed ultrasound beam has the same intensity at different times during the pulse.

True or False: A pulsed ultrasound beam has the same intensity at different times during the pulse.

• A. True
• B. False
• C. Always
• D. Never

Answer: (B)

In a pulsed ultrasound burst, the pressure wave keeps oscillating as the pulse plays out. Intensity depends on the square of pressure, so as the wave rises and falls each cycle, the instantaneous intensity goes up and down. The on-time contains these cycles, reaching a peak when the pressure is at a crest and dropping toward zero as it crosses zero, and there’s typically an off-time between bursts as well. Because of these fluctuations, the beam does not have the same intensity at different moments during the pulse. The average or time-averaged intensity is lower than the peak value, which is why the statement is false.

In a pulsed ultrasound burst, the pressure wave keeps oscillating as the pulse plays out. Intensity depends on the square of pressure, so as the wave rises and falls each cycle, the instantaneous intensity goes up and down. The on-time contains these cycles, reaching a peak when the pressure is at a crest and dropping toward zero as it crosses zero, and there’s typically an off-time between bursts as well. Because of these fluctuations, the beam does not have the same intensity at different moments during the pulse. The average or time-averaged intensity is lower than the peak value, which is why the statement is false.