In continuous ultrasound, spatial peak intensity is determined by which parameter?

In continuous ultrasound, spatial peak intensity is determined by which parameter?

• A. Duty cycle
• B. Beam uniformity ratio (BNR)
• C. Water temperature
• D. Frequency

Answer: (B)

Spatial peak intensity is about the highest intensity found anywhere in the ultrasound beam. Real beams aren’t perfectly uniform, so there are hot spots within the beam. The beam nonuniformity ratio (BNR) captures how much those peak spots can exceed the average along the beam. In other words, BNR tells you how large the spatial peak can be relative to the spatial average, so it largely determines the spatial peak intensity for a given setting (Isp ≈ Iavg × BNR). Water temperature and frequency or duty cycle influence other aspects (like tissue heating patterns, penetration, or duty-cycle effects) but not this fundamental relationship between peak value and beam uniformity.

Spatial peak intensity is about the highest intensity found anywhere in the ultrasound beam. Real beams aren’t perfectly uniform, so there are hot spots within the beam. The beam nonuniformity ratio (BNR) captures how much those peak spots can exceed the average along the beam. In other words, BNR tells you how large the spatial peak can be relative to the spatial average, so it largely determines the spatial peak intensity for a given setting (Isp ≈ Iavg × BNR). Water temperature and frequency or duty cycle influence other aspects (like tissue heating patterns, penetration, or duty-cycle effects) but not this fundamental relationship between peak value and beam uniformity.