39
Ultr
asound Saf
ety Consider
ations
De
fi
nition of Terms
I
SPTA.3
The derated spatial peak temporal average intensity
I
SPPA.3
The derated spatial peak pulse average intensity
I
SATA
The spatial average temporal average intensity
MI
The mechanical index
Pr
.3
The derated peak rarefactional pressure
W
o
The ultrasonic power
f
c
The acoustic center frequency
z
sp
The axial distance at which the reported parameter is measured
x
-6
y
-6
respectively the in-plane (azimuthal) and out-of-plane (elevational)
-6dB dimensions in the x-y plane where z
sp
is found
PD
Pulse
duration
PRF
Pulse repetition frequency
EBD
Entrance beam dimensions for the azimuthal and elevational planes
Statistical Analysis of Measurement Data
Table 3
contains the results from a statistical analysis performed on the acoustic
output data to examine the upper output limit, based on a one sided tolerance
limit approach. The mean and standard deviation of the Spatial-Peak, Time-
Average Intensity and Mechanical Index were found, and the upper output limits
were calculated from the following formula:
X = + KS
x
Where
X
is the upper output parameter limit, , is the average of the measured
output parameter, S
x
is the standard deviation of the measured output
parameter, and K is a factor from the following reference ; M. G. Natrella,
Experimental Statistics, NBS Handbook 91, 1963. K is chosen such that there is
90% confi dence that the output levels of 90% of all units will not exceed the limit
X.
Table 3: Example of Statistical Measurement Data
Probe: SF1-US
Acoustic Output
Pulsed Doppler*
Parameter
I
SATA
@ Transducer
Face / DF [mW/cm
2
]
MI
I
SPTA.3
[mW/cm
2
]
Sample Size
3
3
3
K
4.258
4.258
4.258
Mean
13.1
0.0182
2.53
Standard Deviation
0.406
1.88E-3
0.496
Limit (X)
14.8
0.0261
4.64
Summary of Contents for SONICAID FREEDOM SF1-EUR
Page 1: ...SF1 EUR...
