Appendices
T3300 Diagnostic Ultrasound System | 119 | B00601-010 4/10/17
11.4 Appendix D: Acoustic Output Reporting Tables for Track 3
We follow Track 3 of the FDA’s information for manufacturers seeking marketing clearance of
diagnostic ultrasound systems and transducers. All table entries have been obtained at the same
operating conditions that give rise to the maximum index value. Due to the complexities of the
system user interface, it may be difficult to exactly replicate the declared condition. For more
information, contact BenQ Medical Technology.
11.4.1 Definition of Terms Used in Acoustic Output Tables
Symbols used in the tables are described below:
: Acoustic attenuation coefficient is the coefficient intended to account for ultrasonic attenuation of
tissue between the source and a specified point.
A
aprt
: -12 dB output beam area is the area of the ultrasonic beam derived from the -12 dB output
beam dimensions.
C
MI
: Normalizing coefficient 1 MPa MHz
-1/2
D
eq
: Equivalent aperture diameter is the diameter of a circle whose area is the -12dB output beam
area and given by D
eq
= .
d
eq
: Equivalent beam diameter is the value of the diameter of the acoustic beam at the distance z, in
terms of the equivalent beam area, and given by d
eq
(z) = .
f
awf
: Acoustic working frequency is the arithmetic mean of the most widely separated frequencies f
1
and f
2
at which the amplitude of the pressure spectrum of the acoustic signal is 3 dB lower than the
peak amplitude.
I
pa
: Pulse-average intensity is the ratio of the pulse-intensity integral I
pi
to the pulse duration t
d
.
I
pa, Į
: Attenuated pulse-average intensity is the value of the acoustic pulse-average intensity after
attenuation and at a specified point and given by I
pa, Į
= I
pa
(z)10
(-Įzf
awf
/10)
.
I
spta
: Spatial-peak temporal-average intensity
I
spta, Į
: Attenuated spatial-peak temporal-average intensity
MI: Mechanical index is given by MI = .
n
pps
: Number of pulses per ultrasonic scan line
P: Output power is the time-average power radiated by an ultrasonic transducer into an
approximately free field under specified conditions in a specified medium, preferably water.
P
Į
: Attenuated output power is the value of the acoustic output power after attenuation, at a
specified distance from the transducer, and given by p
Į
= p10
(-Įzf
awf
/10)
.
p
i
: Pulse-pressure-squared integral is the time integral of the square of the instantaneous acoustic
pressure at a particular point in an acoustic field integrated over the acoustic pulse waveform.
pii: Pulse-intensity integral
pii
Į
: Attenuated Pulse-intensity integral
p
r
: Peak-rarefactional acoustic pressure is the maximum of the modulus of the negative
instantaneous acoustic pressure in an acoustic field during an acoustic repetition period.
p
r, Į
: Attenuated peak-rarefactional acoustic pressure is the value of the peak-rarefactional acoustic
pressure after attenuation, at a specified point, and given by p
r, Į+
(z) = p
r
(z)10
(-Įzf
awf
/20)
.
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