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

555

 

 

5.2\ Middle Cerebral Artery (MCA)

Fig. 13.56  Umbilical artery is sampled and measured in this image, the upward spectrum is Doppler waveform of umbilical artery, and the downward spectrum represents Doppler waveform of umbilical vein

5.2.1\ Doppler Sampling

and Waveform of MCA

Scanning Method

The probe is moved downward the head circumference section to show the cranial base structures, and then open the color flow imaging function to show the Willis arterial ring.

Section Structures

The MCA is on one side of Willis arterial ring flowing inclined outward and forward. Its Doppler waveform is shown as single peak shape.

Measuring Method

Doppler sampling gate is placed on unilateral MCA where the arterial segment is close to Willis arterial ring. The direction of the vessel should be observed, and the sampling angle is adjusted to be smaller than 60° (best to be smaller than 45°).

Clinical Significance

(1) It is used to investigate the possibility of fetal intrauterine hypoxia. The resistance of MCA declines when the fetus is in early intrauterine hypoxia. But the resistance of MCA elevates when the fetus is in decompensated intrauterine hypoxia. (2) It is helpful in monitoring fetal

556

YQ. Zhou et al.

 

 

growth and development. The resistance of umbilical artery elevates when there was severe fetal intrauterine growth retardation, and the peak systolic velocity of MCA which is related to hypoxemia and hypercapnia elevates too. (3) It is also used to predict fetal anemia. When peak systolic velocity (PSV) of MCA elevates and is larger than 1.35MoM ~ 1.5MoM, sensitivity of MCA-PSV to predict fetal anemia is approxi-

mately 84 ~ 100%, but the false positive rate is about 10 ~ 12%.

Normal Reference Values

Pulsatility index and resistance index of MCA reduce with the growth of gestational weeks, so does S/D ratio (peak systolic velocity to end-­ diastolic velocity ratio), but the peak systolic velocity elevates with gestation.