User's Manual

140 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/s
ec
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.