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Operation Manual
The maximum derated and the maximum water values do not always occur under the same operating
conditions; therefore, the reported maximum water and derated values may not be related to the In
Situ (derated) formula. For example, a multi-zone array transducer that has the greatest water value
intensities in its deepest zone. the same transducer may have its largest derated intensity in one of its
shallowest focal zones.
Acoustic Output and Measurement
Since the rst usage of diagnostic ultrasound, the possible human biological eects (bioeects)
of ultrasound exposure have been studied by various scientic and medical institutions. In
October 1987, the American Institute of Ultrasound in Medicine(AIUM) ratied a report prepared
by its Bioeects Committee (Bioeects Considerations for the Safety of Diagnostic Ultrasound, J
Ultrasound Med., Sept. 1988: Vol.7, No.9 Supplement), sometimes referred to as the Stowe Report,
which reviewed available data on the possible eects of ultrasound exposure. Another report
“Bioeects and Safety of Diagnostic Ultrasound”, dated January 28, 1993, provides more up to date
information.
The acoustic output for this system has been measured and calculated in accordance with the
December 1985 “510(K) Guide for Measuring and Reporting Acoustic Output of Diagnostic
Ultrasound Medical Devices”, except for the hydrophone, which meets the requirements of “Acoustic
Output Measurement Standard for Diagnostic Ultrasound Equipment” (NEMA UD 2-1992).
The terms and symbols used in the acoustic output tables are dened in the following paragraphs.
ISPTA.3 Derated spatial-peak temporal-average intensity (milliwatts per square
centimeter).
ISPPA.3 The derated spatial-peak pulse-average intensity (watts per square centimeter).
The value of IPA.3 at the position of global maximum MI (IPA.3@MI) may be reported
instead of ISPPA.3 if the global maximum MI is reported.
MI The Mechanical Index. The value of MI at the position of ISPPA.3, (MI@ISPPA.3) may
be reported instead of MI (global maximum value) if ISPPA.3 is 190W/cm
2
.
Pr.3 The derated peak rarefactional pressure (megapascals) associated with the transmit
pattern giving rise to the reported MI value.
WO The ultrasonic power (milliwatts). For operating conditions giving rise to ISPTA.3, WO
is the total time-average power. For operating conditions subject to reporting under
ISPPA.3, WO is the ultrasonic power associated with the transmit pattern giving rise
to the value reported under ISPPA.3.
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