Optimizing the Image
5-92 LOGIQ 7 Online Help
Direction 2392536-100 Rev. 1
Doppler Display
Time zero (the start of the trace) appears on the left side of the
graph. As time progresses, the trace moves to the right. The
baseline of the graph (representing zero velocity, zero frequency
shift, or no detected flow), appears as a solid line running
horizontally across the display. By convention, movement
toward the probe is positive and movement away from the probe
is negative. Positive frequencies or velocities appear above the
baseline. Negative frequencies or velocities appear below the
baseline.
Typically, blood flow is not uniform but is composed of a mix of
blood cells moving at different velocities and in different
directions. Thus, the display is composed of a spectrum as gray
scale values. Strong signals are displayed as bright while weak
signals are displayed as varying shades of gray.
HPRF is invoked when you are operating in PW Doppler Mode
and conditions activate HPRF (when the velocity scale factor or
sample volume gate depth exceeds certain limits). When HPRF
is active, multiple sample volume gates appear along the
Doppler mode cursor. Doppler information can be received from
any of the multiple sample volume gates. The Doppler signals
from all the gates are added together and displayed in one
spectrum.
Information about the PW Doppler display is automatically
written on the screen and updated when scanning parameters
are changed.
This chapter includes:
• A discussion of PW Doppler.
• Activating Pulsed Wave Doppler.
• Optimizing the Doppler spectrum.
Imaged Doppler
When you view the PW Doppler spectrum and a B-Mode image
with a 3.5 MHz probe, this means that you are viewing the
image at 3.5 MHz and `Dopplering' at 2.5 MHz.
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