Which statement best describes the effect of non-thermal ultrasound on cellular processes?

• A. Heats deep tissues to promote collagen deposition.
• B. Enhances cellular signaling and promotes tissue repair through mechanical effects like cavitation and micro-streaming.
• C. Has no effect on cellular processes.
• D. Causes irreversible tissue damage at standard therapeutic doses.

Answer: (B)

Non-thermal ultrasound works mainly through mechanical effects at the tissue level, not by heating. When used in pulsed, low-intensity modes, it creates forces such as micro-streaming and stable cavitation around microbubbles. These mechanical actions can alter cell membranes and activate intracellular signaling pathways, which in turn promote tissue repair processes like fibroblast activity, collagen synthesis, and angiogenesis. This is why it’s described as enhancing cellular signaling and supporting healing through mechanical effects.

Heating deep tissues (the thermal effect) is a different modality of ultrasound, used to promote tissue changes via temperature rise, so that description doesn’t fit non-thermal use. Saying there’s no effect on cells contradicts the evidence that mechanical energy from non-thermal ultrasound modulates cellular activity. Finally, implying it causes irreversible tissue damage at standard therapeutic doses is not accurate for typical therapeutic settings, which aim to avoid damage while providing safe mechanical stimulation.