Int J Gynecol Obstet, 1991, 35: 139-145 International


of Gynecology


and Obstetrics

Fetal intracranial arterial hemodynamics pulsed Doppler ultrasound

assessed by color and

K. Hata, T. Hata, K. Makihara,

and M. Kitao


of Obstetrics and Gynecology.

S. Aoki, 0. Takamiya

Shimane Medical


Izumo 693 (Japan)

(Received November 22nd, 1989) (Revised and accepted March 5th, 1990)



Fetal intracranial arterial velocimetries were serially performed on 31 pregnant women with regular menstrual cycle, at 2840 weeks of gestation, using color andpulsed Doppler ultrasound. The change in fetal intracranial arterial hemodynamics was based on the calculation of resistance index (RI). There was no significant difference between the RI values in the anterior cerebral artery (ACA) and middle cerebral artery (MCA) from 28 weeks to term. The RI in the posterior cerebral artery (PCA) was significantly lower than that in the ACA and MCA, respectively, from 28 weeks to term (P < 0.001). The PI values in both the ACA and MCA remained unchanged from 28 to 33 weeks, became significantly lower from 34 to 35 weeks (P < 0.05), and the values were fairly constant thereafter. The RI seen in the PCA showed no significant change from 28 weeks to term. This color and pulsed Doppler ultrasound assessment offetal intracranial arterial bloodflow provides a useful foundation for elucidating normal intracranial hemodynamics and will aid in avoiding misinterpretations of the different intracranial arteries.

Doppler ultrasound has been widely used for noninvasive investigations to detect various blood flow conditions in normal and pathological pregnancies [2,3,11]. Recent technical and systemic developments have facilitated the study of blood flow velocities in fetal intracranial arteries and characteristics of fetal intracranial arterial hemodynamics have been gradually revealed [ 1,4,14--l 61. However, it is difficult to determine with certainty whether the Doppler signals derive from the main trunk of the internal carotid artery or from the very proximal parts of the circle of Willis [5]. The close signals detected in the fetal head can lead to different interpretations [6]. We report here our findings on each fetal intracranial artery, determined using color and pulsed Doppler ultrasound.

Keywords: Color and pulsed Doppler ultrasound; Intracranial arterial hemodynamics; Fetus; Assessment.

1991 International


Federation and Printed in Ireland

One hundred and ten examinations were performed on 31 normal fetuses, ranging from 28 to 40 weeks of gestation. The mean number of scans per fetus was 3.55. Informed consent for the study was obtained from each mother. One scanning was done on each fetus, at 28-29 weeks, 30-31 weeks, 32-33 weeks, 3G35 weeks, 36-37 weeks and 38-40 weeks of gestation, respectively. Data on factors related Clinical and Clinical

0020-7292/91/%03.50 0

Materials and methods

of Gynecology

and Obstetrics



Hata et al.

modes, velocities can be measured up to 6.2 m/s. Wall filters (100 Hz) were used to eliminate lowfrequency signals occurring from all noise and the sampling volume was set at 1 mm. With the mother placed in a semi-Fowler’s position, we first imaged color flow in the circle of Willis, using the color Doppler mode, at the level of midbrain in the transverse view of the fetal head. Next, the transducer was moved until blood flow in the anterior cerebral artery (ACA), middle cerebral artery (MCA) and posterior cerebral artery (PCA) could be clearly visualized at each arterial pathway, respectively. The sampling volume on the line of pulsed Doppler beam was then placed at the region of interest. Each point was the area where the ACA curved medially and forward above the anterior clinoid process (Fig. la), the

to menstruation and ultrasound estimation of gestational age, by measuring biparietal diameter [8] and fetal femur length [12] were obtained. All were normal infants, delivered vaginally at term and birthweights were within normal ranges (between the 10th and 90th percentile) to the standard intrauterine growth curve for the Japanese infants [lo]. The apparatus used in our study was an Aloka SSD-870 with a 3.5 MHz transducer. Either the color and/or pulsed Doppler modes can be used. The flow directed toward the transducer is displayed in red and the flow directed away from the transducer is in blue. Pulse repetition of this apparatus was 4-26 kHz. Blood flow velocities were displayed within a 28-80” sector, at a depth ranging from 4 to 22 cm. In the color and pulsed Doppler

Fig. la.


color flow mapping

In; J Gynecol Obstet 35

of the anterior




and its velocity


Fetal intracranial arterial hemodynamics

Fig. lb.


Doppler color flow mapping of the middle cerebral artery (arrow) and its velocity waveforms.

MCA ran laterally along the Sylvian fossa (Fig. 1b), and the PCA circled posterolaterally along

the cerebral peduncle (Fig. lc), respectively. Blood flow velocity waveforms were displayed in real time on a monitor oscilloscope and recorded on glossy black on white electrostatic paper at a speed of 50 mm/s. The formula used was resistance index (RI), which is defined as the ratio of the difference between maximum systolic frequency and minimum end-diastolic frequency to maximum systolic frequency [9] calculated as average value obtained from 5 consecutive waves. The differences in the values of RI among each artery in the same gestational periods were analysed by paired t-test, and those among each

gestational period in the same arteries were done by unpaired t-test, respectively. Results

In 96 examinations (87.3% of the examinations), all three arteries could be clearly visualized with the aid of color flow mapping, and blood flow velocity waveforms from each artery were recorded (Fig. 1). In case of failure of detection, the fetal head was occipito-anterior, occipito-posterior position or engaged. Table 1 summarizes the RI values in each artery at each gestational period and Fig. 2 graphically shows the transition of RI after 28 weeks of gestation. No significant difference Clinical and Clinical Research


Hata et al.

Int J Gynecol Obstet 35

Fetal intracranial







G 7




ACA MCA -a : PCA * D

Fetal intracranial arterial hemodynamics assessed by color and pulsed Doppler ultrasound.

Fetal intracranial arterial velocimetries were serially performed on 31 pregnant women with regular menstrual cycle, at 28-40 weeks of gestation, usin...
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