Добавил:
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Atlas of Human Body Ultrasound Scanning_ Methods and Diagnostic Applications ( PDFDrive ).pdf
Скачиваний:
177
Добавлен:
29.07.2022
Размер:
40.13 Mб
Скачать

13  Normal Pregnancy

551

 

 

5\ Doppler Sampling

and Measurement

5.1\ Umbilical Artery

Fig. 13.53  Gray-scale image of sagittal section of umbilical cord. UV umbilical vein, UA umbilical artery

UV

UA

552

5.1.1\ Longitudinal Scanning

of Umbilical Cord

Fig. 13.54  Color Doppler flow image of sagittal section of umbilical cord. UV umbilical vein, UA umbilical artery

YQ. Zhou et al.

13  Normal Pregnancy

553

 

 

5.1.2\ Longitudinal Scanning of

Umbilical Cord with Color

Doppler Image

Fig. 13.55  Gray-scale image of short axis section of umbilical cord. UV umbilical vein, UA umbilical artery

UV

UA

554

YQ. Zhou et al.

 

 

5.1.3\ Transverse Scanning

of Umbilical Cord

5.1.4\ Doppler Sampling and

Waveform of Umbilical Cord

Scanning Method

Umbilical cord could be found in the amniotic fluid, as well as the placental end or the fetal umbilicus end.

Section Structures

There are two smaller umbilical arteries and one larger umbilical vein in the cord. The internal vessels are spiraled in sagittal section. In transverse section, shown by color flow imaging, the blood flows in the two arteries are in the opposite direction of that in the vein. The waveform of the umbilical artery is shown as unimodal type, while the absence of diastolic velocity could be seen in normal first trimester or early stage of second trimester.

Measuring Method

Doppler sampling gate is placed on the umbilical artery; the Doppler waveform of it is detected.

The sampling gate could be magnified properly to show the Doppler waveforms of the umbilical artery and vein at the same time. The probe is moved to make the angle between the umbilical arterial direction and the ultrasonic beam smaller than 45°. The requirements of adjusting angle are underdemanding, if the sampling aim is to acquire pulsatility index and resistance index of umbilical artery.

Clinical Significance

The distant resistance of fetal umbilical artery can be surveyed by Doppler sampling. It is elevated when fetal intrauterine hypoxia happens. The absence or reverse of end-diastolic umbilical arterial blood flow may be shown when the fetus is in severe intrauterine hypoxia. Resistance of umbilical artery elevates also, when severe fetal intrauterine growth retardation occurs.

Normal Reference Values

Pulsatility index and resistance index of umbilical artery decline with the growth of gestational weeks, so does S/D ratio (peak systolic velocity to end-diastolic velocity ratio).