50
Chapter 3
April 2017
bk3500 User Guide
(16-01410-EN-04)
Geometric Measurements
2D Measurements
The geometric measurements performed by BK Ultrasound systems are distance,
perimeter, area and ellipsoid volume. The accuracy of these measurements is
influenced by the following factors:
•
Transducer geometry
•
Rounding of results
•
Resolution of digital image memory
Time Measurements
In M-mode and spectral Doppler mode, data is displayed along a time axis. It is
possible to measure time differences. The accuracy for a time difference
measurement is:
•
Rounded to the nearest: 0.01s
•
Accuracy: 0.01 x
t
where
t
is the full time scale of the image field.
Doppler Measurements
In measuring blood flow velocity it is assumed that the measured power spectral
distribution of the Doppler signal equals the blood cell velocity distribution.
The measurement accuracy of blood flow velocity is heavily dependent on the angle
between the ultrasound beam and the velocity vector of the blood cells. The
velocity accuracies given in the Technical Data (BZ2100) are valid for
= 55
. To
find the percentage accuracy for other angles, multiply the stated accuracy by
If the blood velocity exceeds the selected velocity range, aliasing occurs,
corresponding to an overload condition of the measurement system.
cos
1,8
+
cos
–
cos
------------------------------------------------
100 0,5
+
