User guide

Chapter 5: Measurement References 75
References
Chapter 5: Measurement References
Measurement accuracy
The measurements provided by the system do not
define a specific physiological or anatomical
parameter. Rather, the measurements are of a
physical property such as distance for evaluation by
the clinician. The accuracy values require that you
can place the calipers over one pixel. The values do
not include acoustic anomalies of the body.
The 2D linear distance measurement results are
displayed in centimeters with one place past the
decimal point, if the measurement is ten or greater;
two places past the decimal point, if the
measurement is less than ten.
The linear distance measurement components have
the accuracy and range shown in the following
tables.
Table 1: 2D Measurement Accuracy and
Range
2D Measure
Accuracy
and Range
System
Tolerance
a
Accuracy
By
Test Method
b
Range (cm)
Axial
Distance
< ±2% plus
1% of full
scale
Acquisition Phantom 0-26 cm
Lateral
Distance
< ±2% plus
1% of full
scale
Acquisition Phantom 0-35 cm
Diagonal
Distance
< ±2% plus
1% of full
scale
Acquisition Phantom 0-44 cm
Area
c
< ±4% plus
(2% of full
scale/smallest
dimension) *
100 plus
0.5%
Acquisition Phantom 0.01-72
0 cm
2
Circumfer-
ence
d
< ±3% plus
(1.4% of full
scale/
smallest
dimension) *
100 plus
0.5%
Acquisition Phantom 0.01-96
cm
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. The area accuracy is defined using the following equation:
% tolerance = ((1 + lateral error) * (1 + axial error) – 1) *
100 + 0.5%.
d. The circumference accuracy is defined as the greater of the
lateral or axial accuracy and by the following equation:
% tolerance = ( (maximum of 2 errors) * 100) + 0.5%.
2