Which intensity is measured over the entire area of the beam and all time?

The intensity measured over the entire area of the beam and all the time is known as the Spatial Average Temporal Average intensity, or SATA. This measurement encompasses both spatial distribution (averaging over the area of the ultrasound beam) and temporal distribution (averaging over the entire duration of time the ultrasound is being emitted).

SATA provides a comprehensive representation of the ultrasound intensity as it accounts for the variations in intensity that can occur not only across the surface of the beam but also throughout the entire scanning period. This makes it particularly useful for evaluating the exposure levels of tissues to ultrasound energy over the duration of the examination.

In contrast, other intensity measurements each focus on different aspects or aspects at specific moments. For instance, the Spatial Peak Temporal Peak intensity (SPTP) focuses on the peak intensity at a specific spot in the beam at its highest moment, while the Spatial Peak Pulse Average (SPPA) measures the peak intensity but averages it over the pulse duration. The Spatial Peak Temporal Average (SPTA) also provides an average intensity but does so over the time of the transmission, making it less comprehensive than SATA when considering overall exposure.