Which statement best describes beam nonuniformity when there is a pronounced hot spot?

Which statement best describes beam nonuniformity when there is a pronounced hot spot?

• A. The beam is perfectly uniform
• B. The SAI significantly exceeds SPI
• C. The SPI is lower than the SAI
• D. The SPI is higher than the SAI

Answer: (D)

A pronounced hot spot means one area of the beam has much higher intensity than the rest. In ultrasound terminology, spatial peak intensity (SPI) is the maximum intensity in the beam, while spatial average intensity (SAI) is the average across the beam. When a hot spot is present, that maximum intensity rises above the average, so SPI is greater than SAI. The ratio SPI/SAI, which reflects beam nonuniformity, becomes greater than 1. If the beam were perfectly uniform, SPI would equal SAI; if SAI exceeded SPI, you’d have a trough rather than a hot spot.

A pronounced hot spot means one area of the beam has much higher intensity than the rest. In ultrasound terminology, spatial peak intensity (SPI) is the maximum intensity in the beam, while spatial average intensity (SAI) is the average across the beam. When a hot spot is present, that maximum intensity rises above the average, so SPI is greater than SAI. The ratio SPI/SAI, which reflects beam nonuniformity, becomes greater than 1. If the beam were perfectly uniform, SPI would equal SAI; if SAI exceeded SPI, you’d have a trough rather than a hot spot.