FujiFilm SonoSite Edge II User Manual page 190

where:
In Situ = In Situ intensity value
Water = Water intensity value
e = 2.7183
a = attenuation factor (dB/cm MHz)
Attenuation factor (a) for various tissue types are given below:
brain = 0.53
heart = 0.66
kidney = 0.79
liver = 0.43
muscle = 0.55
l = skinline to measurement depth in cm
f = center frequency of the transducer/system/mode combination in MHz
Since the ultrasonic path during the exam is likely to pass through varying lengths and types of tissue, it is
difficult to estimate the true In Situ intensity. An attenuation factor of 0.3 is used for general reporting
purposes; therefore, the In Situ value commonly reported uses the formula:
In Situ (derated) = Water [e
Since this value is not the true In Situ intensity, the term "derated" is used to qualify it.
The maximum derated and the maximum water values do not always occur at the same operating conditions;
therefore, the reported maximum water and derated values may not be related by the In Situ (derated)
formula. For example: a multi-zone array transducer that has maximum water value intensities in its deepest
zone, but also has the smallest derating factor in that zone. The same transducer may have its largest derated
intensity in one of its shallowest focal zones.
184
-(0.069lf )
]
Acoustic output measurement