Which change would most likely increase the intensity at the focus of the ultrasound beam?

• A. Increasing focusing
• B. Increasing beam area
• C. Decreasing acoustic output
• D. Decreasing receiver gain

Answer: (A)

Concentrating energy into a smaller focal region increases the intensity at the focus. Intensity at the focal point depends on how much acoustic power is delivered and how tightly that power is focused. When focusing is increased, the beam converges more and the focal spot becomes smaller. With the same transmitted power, a smaller area means higher energy density, so the peak intensity at the focus rises. This is why stronger focusing boosts the signal at the focal point.

Expanding the beam area spreads the same power over a larger region, reducing the focal intensity. Decreasing acoustic output lowers the total emitted power, directly reducing the intensity at the focus. Decreasing receiver gain only affects the amplification of received echoes, not the emitted beam’s intensity at the focus.