GE Medical Systems 500, User Manual, Page: 174 / 636

Doppler
LOGIQ 500 Basic Users Manual
2276612–100 Rev. 0
5–62
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Controls (cont’d)
CFM/Spectrum Invert Baseline Shift
Description
Vertically inverts the spectrum trace
without affecting the baseline position. Changes the spectrum baseline to
accommodate higher velocity blood flow.
Minimizes aliasing by displaying a greater
range of forward flow than reverse flow.
With baseline shift, higher velocities in one
direction can be displayed without clipping
off the peaks.
Accessing/
Changing Forward flow (F) and Reverse flow (R)
signs appear on the velocity scale which
reverse when the spectrum is inverted.
Positive velocities go to the bottom of the
spectrum and to the right speaker. A
spectral invert graphic appears on the
display to indicate that the spectrum has
been inverted.
NOTE: Inverting the spectrum does not
affect the baseline position.
Baseline shift adjusts the point in the
spectrum where the velocity trace is at
zero. The default baseline can be chosen
in the Set Up/Custom Display menu
page 17.
The baseline is displayed as a solid line
running across the spectrum. The
baseline is raised and lowered in equal
increments, depending on the current
Doppler scale factor.
The control does not wrap when the
maximum baseline shift (in either direction)
has been reached. This is a non-repeating
key.
Benefits If the blood flow is still moving in the same
direction after changing the probe angle,
the Doppler information may be reversed.
It is easy to invert the spectrum instead of
reversing the probe orientation. Unwraps the alias. Rearranges the
velocity scale display without changing the
velocity scale. Readjusts the positive and
negative velocities limit without changing
the total velocity range.
Values –75%, –50%, –25%, 0, +25%, +50%, and
+75%, with zero being the center of the
display, +100% being the top edge of the
display and –100% being the bottom edge
of the display.
Affects on
Other Controls The polarity of the audio Doppler is also
reversed.
When “Spec. Inv. in Triplex” preset on
Custom Display page 16 is set to
Simultaneous, the CFM spectrum is also
inverted.