GE LOGIQ 500 Advanced Reference Manual page 196

Bioeffects
Uterine artery (cont'd)
Fetal heart
6–12
For pulsed Doppler systems, place the transducer in the lower
outer portion of the maternal abdomen. The orientation should
be towards the parametria with some parts of the amniotic sac
visualized. The parametria area can then be examined by
maneuvering the sample volume until the characteristic
waveforms are obtained. Examination should be confined to the
area that is composed of the myometrium and may be most
fruitful close to the placenta. Indices of pulsatility, if calculated,
should be determined for each of several heartbeats and
averaged.
Fetal cardiac Doppler studies can be performed only with
duplex ultrasound systems. The fetal heart should be carefully
examined in all standard planes to determine whether or not the
anatomy is normal. These planes should include: four
view, long axis left ventricles, short axis of the ventricles, short
axis of the great vessels, aortic arch, and pulmonary
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artery ductus views. The area for sampling should be visualized
as clearly as possible with the anticipated flow direction at as
low an angle as possible to the ultrasound beam. The sample
volume should be placed in this area with an appropriate size
selected to sample as desired. Power output control should be
at the lowest setting compatible with obtaining an adequate
image and the gain setting should be maintained to keep an
adequate signal without excessive noise. Excluding the actual
valves from the sample volume will help to minimize
unnecessary noise from the signals obtained.
LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0
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chamber