Which statement about ultrasound intensity is incorrect?

Which statement about ultrasound intensity is incorrect?

• A. It influences the rate of heating.
• B. It is usually greatest in the center of the beam.
• C. It influences the depth of penetration.
• D. It is measured in W/cm2.

Answer: (C)

Ultrasound intensity is the power delivered per unit area to tissue, and it governs the thermal effects produced by the beam. The higher the intensity, the more energy is deposited in the tissue, leading to faster heating. Within the ultrasound beam, the intensity is greatest in the center (the focal region) and diminishes toward the edges, creating a center-heavy profile. Penetration depth, however, is determined mainly by frequency and tissue attenuation. Lower frequencies penetrate deeper because they experience less absorption and scattering, whereas higher frequencies are absorbed more quickly and don’t reach as far. Therefore, changing intensity doesn’t dictate how deep the ultrasound travels; it affects how much energy—and thus heating—is delivered within the beam’s path. Measuring intensity in watts per square centimeter (W/cm²) reflects this power-per-area concept. So the statement that intensity influences depth of penetration isn’t correct; it’s the frequency and tissue properties that set how deep the ultrasound goes. The other points—intensity driving heating, being highest at the beam center, and being expressed in W/cm²—are accurate.

Ultrasound intensity is the power delivered per unit area to tissue, and it governs the thermal effects produced by the beam. The higher the intensity, the more energy is deposited in the tissue, leading to faster heating. Within the ultrasound beam, the intensity is greatest in the center (the focal region) and diminishes toward the edges, creating a center-heavy profile.

Penetration depth, however, is determined mainly by frequency and tissue attenuation. Lower frequencies penetrate deeper because they experience less absorption and scattering, whereas higher frequencies are absorbed more quickly and don’t reach as far. Therefore, changing intensity doesn’t dictate how deep the ultrasound travels; it affects how much energy—and thus heating—is delivered within the beam’s path.

Measuring intensity in watts per square centimeter (W/cm²) reflects this power-per-area concept. So the statement that intensity influences depth of penetration isn’t correct; it’s the frequency and tissue properties that set how deep the ultrasound goes. The other points—intensity driving heating, being highest at the beam center, and being expressed in W/cm²—are accurate.