Huntleigh FD2 - Page 40

40
Acoustic Safety (continued)
Acoustic intensity data (I
SPTA.3
) for probes available for use with the FD1+,FD2 & FD3
are summarized in the following table. The values cited are based on measurements
in water using a calibrated hydrophone and are stated as the estimated derated
intensities. The derated intensity constitutes the most biologically relevant parameter
available since true determinations of actual absorbed dose in tissue would require
invasive measurement techniques. The derated intensity is therefore calculated
mathematically using a derating factor consisting of a constant (the assumed
attenuation coefficient) and allowing for the frequency of the probe and the distance
from the probe face to the hydrophone.
The calculated derated intensity values for the FD1+,FD2 & FD3 compare very favorably
with previously reported acoustic safety data for Doppler ultrasound instruments and are
appropriate for all clinical applications recommended in this manual.
As the operating mode of the Dopplex range of probes is continuous wave, I
SPPA
figures are not applicable.
WWAARRNNIINNGG//CCAAUUTTIIOONNSS && SSAAFFEETTYY
1.2 x 2.5
1.2 x 2.5
0.365 x 0.8
0.365 x 0.8
0.215 x 0.5
0.635 x 0.22
0.215 x 0.5
EBD
OP2 HS
OP3 HS
VP4 HS
VP5 HS
VP8 HS
EZ8
VP10 HS
Model
Acoustic Output Table, Track1, Non-Auto-Scanning Mode
Max. Value
I
SPTA.3
Wo
f
cc
Z
sspp
A-66,
(Z
sspp
)
55
55
92
92
92
92
92
41
32
7.5
8.2
4.0
14.3
1.4
2.0
3.0
4.0
5.0
8.0
8.0
10.0
2.5
2.0
0.8
0.8
0.48
0.67
0.48
1.1
1.2
0.14
0.12
0.026
0.064
0.022
NOTES
1. Measurement uncertainty: varies with probe and measurement
Random - typically ±20% (max. ±32%)
Systematic - typically ±6.5% (max. ±8%)
Definnitionn of Terrmms
I
SPTA.3
is the derated spatial-peak, temporal-average intensity (milliwatts
per square centimeter)
Wo
is the ultrasonic power (milliwatts)
f
c
is the center frequency (MegaHertz)
Zsp
is the axial distance used to calculate the derated intensity (centimeters)
A-66 (Z
sp
)
is ( /4) x (X-6 x Y-6) where X-6, Y-6 are respectively the in-plane
(azimuthal) and out-of-plane (elevational) -6dB dimensions in the X-Y
plane where Zsp is found (centimeters)
EBD
are the entrance beam dimensions for the azimuthal and elevational
planes (centimeters)
EENNGGLLIISSHH
((UUSSAA))