If a transducer has a high BNR, what adjustment helps minimize hotspots?

• A. Move transducer more rapidly to avoid hot spots
• B. Increase the duty cycle
• C. Move transducer more slowly to focus energy
• D. Decrease frequency

Answer: (A)

Beam nonuniformity ratio (BNR) tells us how uneven the ultrasound beam is in the focal zone. A high BNR means there are strong hotspots where the energy is concentrated. To reduce those hotspots, the practical approach is to move the transducer more rapidly so the beam sweeps across the treatment area. This rapid motion averages the energy over a larger region or time, lowering the peak intensity at any single point and making heating more uniform.

Increasing the duty cycle would deliver more energy at each point and could worsen hotspots. Moving more slowly to focus energy would concentrate heat rather than spread it. Decreasing frequency changes beam properties but doesn’t directly address the nonuniformity issue in the way rapid transducer motion does.