For effective heating with therapeutic ultrasound within a five-minute period, the treated area should be approximately what size relative to the soundhead?

• A. Twice the size
• B. The same size
• C. Half the size
• D. Four times the size

Answer: (A)

Therapeutic ultrasound heats tissue most where the beam is strongest, with a clear drop-off toward the edges. To achieve meaningful heating within a five-minute window, the region you treat should be about twice the size of the transducer’s effective radiating area. This sizing ensures there’s enough energy overlap to heat a broader area effectively without needing to extend the treatment time. If you treat a smaller area, you risk overheating a tiny spot and missing surrounding tissue; treating a much larger area would spread the energy too thin, reducing heating efficiency in the allotted time.