Low-dose ultrasound can be used over which of the following areas?

• A. Metal implants and growth plates
• B. Tendons
• C. Nerves
• D. Cartilage

Answer: (A)

Low-dose ultrasound is used with safety margins in mind, relying on non-thermal effects and minimal risk to surrounding tissues. When energy is kept very low and delivered in pulsed form, areas that interact with the sound waves in predictable ways can tolerate the treatment well.

Metal implants and surrounding tissue respond to ultrasound energy differently because metal has a much higher acoustic impedance than soft tissue. This causes most of the ultrasound energy to reflect at the implant interface, so little energy reaches the tissues near the implant, reducing the chance of heating or tissue disruption. That makes it acceptable to apply low-dose ultrasound over joints or areas with hardware.

Growth plates are cartilaginous regions in children that are often of concern with higher-energy modalities. At low-dose, pulsed settings, the energy is not enough to cause harm while still providing potential therapeutic effects, so these areas can also be treated cautiously with ultrasound.

Tendons, nerves, and cartilage can be treated with ultrasound under appropriate settings, but the scenario described emphasizes safety in regions with implants or developing bone, which is why this area is highlighted as appropriate for low-dose ultrasound.