Philips EPIQ 7 User Manual page 61

Biological Safety
Ultrasound in Medicine, Vol. 7, No. 9 Supplement, September 1988), sometimes referred to as
the Stowe Report, which reviewed available data on possible effects of ultrasound exposure.
Another report, "Bioeffects and Safety of Diagnostic Ultrasound," dated January 28, 1993,
provides more-current information.
The acoustic output for this system has been measured and calculated in accordance with the
"Acoustic Output Measurement Standard for Diagnostic Ultrasound Equipment" (Revision 3,
AIUM, NEMA, 2004), the "Standard for Real-Time Display of Thermal and Mechanical Acoustic
Output Indices on Diagnostic Ultrasound Equipment" (Revision 2, AIUM, NEMA, 2004), and the
September 2008 FDA document "Information for Manufacturers Seeking Marketing Clearance
of Diagnostic Ultrasound Systems and Transducers."
In Situ, Derated, and Water Value Intensities
All intensity parameters are measured in water. Since water absorbs very little acoustic energy,
these water measurements represent a worst case value. Biological tissue does absorb acoustic
energy. The true value of the intensity at any point depends on the amount and type of tissue
and the frequency of the ultrasound that passes through the tissue. The intensity value in the
tissue, In Situ, has been estimated by using the following formula:
In Situ = Water [e
Where:
Variable
In Situ
Water
e
a
Tissue
Amniotic Fluid
Brain
Heart
Kidney
Liver
Muscle
l
f
EPIQ 7 User Manual 4535 617 25341
]
-0.23alf
Value
In Situ intensity value
Water value intensity
2.7183
Attenuation factor
a(dB/cm-MHz)
0.006
0.53
0.66
0.79
0.43
0.55
Skin line to measurement depth (cm)
Center frequency of the transducer/system/mode combination (MHz)
Safety
61