Doc #: 60-00118 Rev. A
70
Measurements
Accuracy
Range
Mean Velocity
+/- 5%
Calculated Value
Maximum Velocity
+/- 5%
0 to 480 cm/s
Minimum Velocity
+/- 5%
0 to 480 cm/s
Pulsatility Index (PI)
+/- 5%
Calculated Value
Velocity measurement accuracy is presented as a percentage of the measured velocity. It should
be noted that at lower velocities, resolution uncertainty begins to overshadow.
The velocity measurements displayed on the system are derived from a computational analysis
of the spectrogram data. The following is a high-level flow diagram of the calculations:
Sampled Blood Flow Signal:
The System receives the reflected Doppler ultrasound signals from the transmitted beam. The
received Doppler signal is processed based upon the depth and sample volume set by the user.
The output of the processed signal is the measured velocities along the beam path.
Spectrogram:
The System displays the measured velocities on the vertical axis of the spectrogram display. The
System also shows the changes in velocity as a function of time (along the horizontal axis). The
spectrogram velocity accuracy assumes zero Doppler angle and is <+/- 5%. The blood flow
velocity is non-uniform across a vessel. This distribution of velocities on the spectrogram is
complex and the final interpretation remains with the clinician.
Velocity Envelope:
Sampled Blood
Flow Signal
Spectrogram
Velocity Envelope
Velocity
Measurements
