If continuous ultrasound intensity is increased from 1.5 W/cm2 to 2.0 W/cm2, which outcome is MOST likely?

• A. Decrease in the depth of tissue penetration
• B. Decrease in the amount of heating energy delivered
• C. Increase in the depth of tissue penetration
• D. Increase in the amount of heating energy delivered

Answer: (D)

Increasing continuous ultrasound intensity raises the amount of acoustic energy delivered to the tissue, so more energy per unit time is deposited and tissue heating increases. The depth of penetration, however, is mainly determined by the frequency (not intensity): higher frequency heats and attenuates more quickly, leading to shallower penetration, while lower frequency reaches deeper tissues. So boosting intensity does not deepen penetration; it increases heating. Therefore, the most likely outcome is an increase in the amount of heating energy delivered.