Which statement about ultrasound intensity is true?

Which statement about ultrasound intensity is true?

• A. It influences the rate of heating.
• B. It determines the depth of penetration.
• C. It changes the frequency.
• D. It has no relation to heating.

Answer: (A)

Ultrasound intensity is the amount of acoustic power delivered per unit area to the tissue, and that energy is what gets absorbed and converted into heat. So, when intensity is higher, more energy is deposited per second, and the temperature rises more quickly—assuming the duty cycle and exposure duration stay the same. This is why intensity directly influences the rate of heating. Depth of penetration is governed mainly by frequency: lower frequencies penetrate deeper while higher frequencies are absorbed more superficially. You can have the same depth with different intensities, but changing intensity doesn’t change how deep the waves go. The frequency itself is a property of the transducer and isn’t altered by intensity. Finally, the idea that intensity has no relation to heating isn’t accurate, because heating rate increases with greater energy delivery.

Ultrasound intensity is the amount of acoustic power delivered per unit area to the tissue, and that energy is what gets absorbed and converted into heat. So, when intensity is higher, more energy is deposited per second, and the temperature rises more quickly—assuming the duty cycle and exposure duration stay the same. This is why intensity directly influences the rate of heating.

Depth of penetration is governed mainly by frequency: lower frequencies penetrate deeper while higher frequencies are absorbed more superficially. You can have the same depth with different intensities, but changing intensity doesn’t change how deep the waves go. The frequency itself is a property of the transducer and isn’t altered by intensity.

Finally, the idea that intensity has no relation to heating isn’t accurate, because heating rate increases with greater energy delivery.