Which parameter describes the energy delivered by the ultrasound beam per unit area per unit time?

Which parameter describes the energy delivered by the ultrasound beam per unit area per unit time?

• A. Frequency
• B. Intensity
• C. Propagation speed
• D. Depth

Answer: (B)

In ultrasound, the quantity that tells you how much energy crosses a surface per unit time is intensity. Intensity is the power delivered per unit area (units like W/cm²), so it directly measures how much energy the beam delivers to tissue per second over a given cross-section. This is what governs how much heating and how bright an echo will appear, since more energy per area means more energy deposited in the tissue. Frequency describes how often the wave cycles occur each second, and affects resolution and attenuation but not the rate of energy crossing a surface per unit area. Propagation speed is how fast the wave travels through tissue, influencing wavelength and impedance relationships but not the energy flux per area. Depth is simply how far the sound has traveled into the body, not an intrinsic measure of energy delivery.

In ultrasound, the quantity that tells you how much energy crosses a surface per unit time is intensity. Intensity is the power delivered per unit area (units like W/cm²), so it directly measures how much energy the beam delivers to tissue per second over a given cross-section. This is what governs how much heating and how bright an echo will appear, since more energy per area means more energy deposited in the tissue.

Frequency describes how often the wave cycles occur each second, and affects resolution and attenuation but not the rate of energy crossing a surface per unit area. Propagation speed is how fast the wave travels through tissue, influencing wavelength and impedance relationships but not the energy flux per area. Depth is simply how far the sound has traveled into the body, not an intrinsic measure of energy delivery.