User guide

76 Sources of measurement errors
Sources of measurement
errors
In general, two types of errors can be introduced
into the measurement:
Acquisition Error Includes errors introduced by
the ultrasound system electronics relating to signal
acquisition, signal conversion, and signal processing
for display. Additionally, computational and display
errors are introduced by the generation of the pixel
scale factor, application of that factor to the caliper
positions on the screen, and the measurement
display.
Algorithmic Error The error introduced by
measurements, which are input to higher order
calculations. This error is associated with
Table 2: M Mode Measurement and
Calculation Accuracy and Range
M Mode Measurement
Accuracy and Range
System Tolerance
Accuracy By Test Method
Range
Distance < +/-
2%
plus
1% of
full
scale
a
Acquisition
Phantom
b
0-26
cm
Time < +/-
2%
plus
1% of
full
scale
c
Acquisition
Phantom
d
0.01-10
sec
Heart Rate < +/-
2%
plus
(Full
Scale
c
*
Heart
Rate/1
00) %
Acquisition
Phantom
d
5-923
bpm
a. Full scale for distance implies the maximum depth of the
image.
b. An RMI 413a model phantom with 0.7 dB/cm MHz
attenuation was used.
c. Full scale for time implies the total time displayed on the
scrolling graphic image.
d. SonoSite special test equipment was used.
Table 3: PW Doppler Mode Measurement
and Calculation Accuracy and Range
Doppler Mode
Measurement
Accuracy and Range
System
Tolerance
Accuracy By
Test
Method
a
Range
Velocity
cursor
< +/- 2%
plus 1% of
full scale
b
Acquisition Phantom 0.01
cm/sec-
550 cm/
sec
Frequency
cursor
< +/- 2%
plus 1% of
full scale
b
Acquisition Phantom 0.01kHz
-20.8
kHz
Time < +/- 2%
plus 1% of
full scale
c
Acquisition Phantom 0.01-10
sec
a. SonoSite special test equipment was used.
b. Full scale for frequency or velocity implies the total frequency
or velocity magnitude, displayed on the scrolling graphic
image.
c. Full scale for time implies the total time displayed on the
scrolling graphic image.