Which of the following is a nonthermal effect of ultrasound?

Which of the following is a nonthermal effect of ultrasound?

• A. Increase vascular permeability
• B. Decrease metabolic rate
• C. Increase tissue temperature dramatically
• D. Cause permanent cell death

Answer: (A)

Nonthermal effects of ultrasound arise from mechanical energy rather than heating. The waves produce micromechanical phenomena such as cavitation and microstreaming, which can temporarily alter cell membranes and the walls of tiny blood vessels. Increasing vascular permeability is a classic example: the mechanical forces loosen intercellular junctions and make capillary walls more permeable, facilitating fluid and nutrient exchange to support the healing process without a sustained rise in temperature. In contrast, dramatically increasing tissue temperature describes the thermal effect, which is a different mechanism. Ultrasound causing permanent cell death would be an extreme, non-therapeutic outcome and not a typical nonthermal effect. A decrease in metabolic rate isn’t a primary consequence attributed to standard therapeutic ultrasound.

Nonthermal effects of ultrasound arise from mechanical energy rather than heating. The waves produce micromechanical phenomena such as cavitation and microstreaming, which can temporarily alter cell membranes and the walls of tiny blood vessels. Increasing vascular permeability is a classic example: the mechanical forces loosen intercellular junctions and make capillary walls more permeable, facilitating fluid and nutrient exchange to support the healing process without a sustained rise in temperature.

In contrast, dramatically increasing tissue temperature describes the thermal effect, which is a different mechanism. Ultrasound causing permanent cell death would be an extreme, non-therapeutic outcome and not a typical nonthermal effect. A decrease in metabolic rate isn’t a primary consequence attributed to standard therapeutic ultrasound.