GE LOGIQ 500 Advanced Reference Manual page 195

Umbilical artery (cont'd)
Uterine artery
LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0
If a duplex Doppler system is being used, then the umbilical
cord should be visualized and attempted to be seen in as much
of its length as is feasible, considering its usual coiling. The
sample volume of the pulsed Doppler or the sample line if a
duplex continuous wave instrument is being used should be
placed over one of the two smaller vessels in the umbilical cord.
The sample volume size ("gate") should be adjusted to
encompass the entire vessel. If this vessel is being seen only in
cross section, and diastolic flow is not seen, this may be an
artifact caused by the angle between the beam and the vessel
and another sampling site should be examined. When this
cross sectional view is obtained, rotating the transducer 90
degrees may bring a greater length of the cord into view and
permit examination of an area where the artery can be seen at
a more advantageous angle. Indices of pulsatility, if calculated,
should be determined for each of several heartbeats and
averaged.
For continuous wave Doppler systems, place the pencil probe
in the lower lateral portion of the mother's abdomen, generally
just above the groin and directed toward the cervix. Adjust the
angle or position until the characteristic waveform of the
uterine/arcuate artery is obtained. Without visualization, it is
important to search carefully for the waveform with the greatest
amount of diastolic flow as proximal vessels in the uterine
system (internal iliac and hypogastric arteries) may have
diminished diastolic flow compared to the systolic flow in a way
that might appear abnormal if obtained from the uterine artery
itself. The power and gain settings should be adjusted to the
lowest levels at which adequate signals are obtained with a
minimal amount of noise relative to the signal. The image may
be frozen when the desired number of waveforms are present
on the screen.
Bioeffects
6–11