Tissues absorb US delivered at 3 MHz at a rate 3x faster than 1 MHz US

Tissues absorb US delivered at 3 MHz at a rate 3x faster than 1 MHz US

• A. slower
• B. the same
• C. faster
• D. unpredictable

Answer: (C)

When frequency rises, tissue attenuates and absorbs energy more rapidly. In soft tissue, the attenuation coefficient increases with frequency, so a 3 MHz wave loses energy per unit depth faster than a 1 MHz wave. This means the rate at which tissue absorbs energy—and thus heats up—is higher at 3 MHz, approximately three times greater if other factors are equal. The side effect is shallower penetration, but the heating occurs more quickly near the surface. So the correct idea is that the tissue absorbs the energy faster at 3 MHz.

When frequency rises, tissue attenuates and absorbs energy more rapidly. In soft tissue, the attenuation coefficient increases with frequency, so a 3 MHz wave loses energy per unit depth faster than a 1 MHz wave. This means the rate at which tissue absorbs energy—and thus heats up—is higher at 3 MHz, approximately three times greater if other factors are equal. The side effect is shallower penetration, but the heating occurs more quickly near the surface. So the correct idea is that the tissue absorbs the energy faster at 3 MHz.