Final answer:
The Beam Nonuniformity Ratio (BNR) describes the variability of ultrasound beam intensity, calculated as the Spatial Peak Intensity (SPI) divided by the Spatial Average Intensity (SAI).
Step-by-step explanation:
The ultrasound characteristic that describes the amount of variability of intensity within the beam is known as the Beam Nonuniformity Ratio (BNR). The BNR is calculated by dividing the Spatial Peak Intensity (SPI) by the Spatial Average Intensity (SAI). The SPI refers to the maximum intensity found within the ultrasound beam, while the SAI represents the average intensity across the entire beam