What is the maximum Beam Uniformity Ratio (BNR) that should not be exceeded in therapeutic ultrasound?

What is the maximum Beam Uniformity Ratio (BNR) that should not be exceeded in therapeutic ultrasound?

• A. 4
• B. 6
• C. 8
• D. 10

Answer: (C)

Beam Uniformity Ratio shows how evenly energy is distributed in the ultrasound beam. It is the ratio of peak intensity to the average intensity across the beam. A lower BNR means a more uniform beam; a higher BNR means more hot spots. In therapeutic ultrasound, you want to limit hotspots to avoid unintended tissue heating. The practical safety limit used is eight-to-one, so the maximum BNR should not exceed this value. Staying at or below this threshold helps ensure the delivered energy stays within safe and predictable bounds. Values below that are more uniform but not required; values above that would increase the risk of local overheating and potential tissue damage, which is why eight-to-one is considered the upper bound.

Beam Uniformity Ratio shows how evenly energy is distributed in the ultrasound beam. It is the ratio of peak intensity to the average intensity across the beam. A lower BNR means a more uniform beam; a higher BNR means more hot spots. In therapeutic ultrasound, you want to limit hotspots to avoid unintended tissue heating. The practical safety limit used is eight-to-one, so the maximum BNR should not exceed this value. Staying at or below this threshold helps ensure the delivered energy stays within safe and predictable bounds. Values below that are more uniform but not required; values above that would increase the risk of local overheating and potential tissue damage, which is why eight-to-one is considered the upper bound.