The nonthermal effect of ultrasound is called?

• A. Micromassage
• B. Heating
• C. Cavitation
• D. Reflection and refraction

Answer: (A)

Nonthermal effects of therapeutic ultrasound are mechanical actions produced by the sound waves rather than heat. Micromassage describes the gentle, micro-scale tissue movement and fluid effects caused by the acoustic pressure, which can stimulate cellular activity and healing without raising tissue temperature. Heating is the thermal effect, resulting from energy absorption and temperature rise. Reflection and refraction are about how the waves propagate and bounce at interfaces, not a tissue-level therapeutic effect. Cavitation is another mechanical phenomenon that can occur, but the term most commonly used to describe the nonthermal action in many therapies is micromassage, making it the best answer here.