Dopplerography of the brain in children

At present, duplex Doppler systems are used in neonatology, which allows to visualize the vessel in the ultrasound section of the brain, to establish a control volume in its lumen and to obtain a dopplerogram reflecting the blood flow in this vessel. Ultrasonic devices with color (energy) Doppler mapping (CDC) allow choosing the optimal position for placing the control volume in large cerebral arteries for measuring the speed with minimal error, and also obtaining an image of the venous vessels of the brain. The advantage of technology of color Doppler energy mapping (EHD) is relative independence from the angle of insonation, as well as the speed and direction of the flow. A significant increase in information capabilities has a three-dimensional reconstruction method, which gives an opportunity to get an idea of the spatial arrangement and form of the vessels. To better characterize the blood flow, especially at low-speed rates, the B-flow method is used.

In neonatology, the most commonly used index of resistance, which determines the peripheral vascular resistance. The index is quite informative, since it does not depend on the diameter of the vessel and the magnitude of the insonation angle. To ensure standard conditions for conducting a Doppler study, the following rules must be adhered to:

1. The study should be carried out under the condition that the newborn remains at rest, preferably in a state of physiological sleep, 1-1.5 hours after feeding, while maintaining optimal body temperature and ventilation regimes.
2. Use a low-pass filter (100 Hz).
3. The dimensions of the control volume are 2-3 mm, which completely closes the lumen of the vessel and avoids the imposition of signals from closely located vessels.
4. The study should be carried out at the minimum values of the angle of insolation.
5. Choose the most straight sections of the vessel, further away from bifurcations to preserve the laminar flow of blood.

Doppler study of blood flow is carried out in the largest arteries of the brain: internal carotid, anterior, middle, posterior and main, which are defined as pulsating echopositive structures. The use of the DCM and / or EHD mode greatly simplifies the search and visualization of arteries.

Anterior cerebral artery. The most convenient and simple position for its detection is the sagittal section through a large fontanel. Usually, the right and left anterior cerebral arteries are located very close to each other, which makes it impossible to distinguish them as separate vessels. Separately, these arteries can be seen by applying the EHD regime. To obtain blood flow indicators, the control volume is set before the knee of the corpus callosum or in the proximal part of the artery before its bending around this structure, with the angle between the axis of the vessel and the ultrasonic beam being minimal.

Internal carotid artery (distal segment). To register the blood flow, use the vertical part of the vessel after its exit from the carotid canal at the level of the Turkish saddle, since further, above the level of the anterior wedge-shaped process, it is divided into the anterior and middle cerebral arteries. 

The main artery. Examine in the middle sagittal section on the front surface of the bridge or in the coronary plane a few millimeters behind the site of the internal carotid artery.

Middle cerebral artery. The main guideline in the search for an artery is the lateral furrow at the border of the frontal and temporal lobes. The most successful angle of its insonation is achieved with the axial approach.

Investigation of all the above arteries in a newborn child is often difficult due to his anxiety, crying and / or severe resuscitation of the child. As a screening, it is permissible to use data obtained only from the anterior cerebral artery, since normally the angular-dependent parameters differ insignificantly in the above vessels. In newborns, the asymmetry of the blood flow parameters in the main arteries of the right and left hemispheres of the brain is not usually detected.

Using devices with EHD function in the coronary plane, one can get a complete picture of the arterial circle of the large brain, including the middle, posterior connective, posterior arteries and proximal parts of both anterior cerebral arteries. When carrying out a Doppler survey, it should be remembered that there are individual differences in the structure of the cerebral vascular system. Therefore, there are no absolute standards for linear blood flow velocity (LSC) in the intracranial arteries, although N. Bode gives a detailed table of these indicators in children from birth to 18 years. Individual features also have a skull and the size of a large fontanel. Therefore, it is recommended to compare the absolute rates of velocities in the dynamics of one child, obtained by the same researcher, on the same device. More reliable are the independent of the angle indices of indices of resistance and pulsation (IR, IP).

The veins of the brain. Although reception of signals of blood flow through large cerebral venous communication of newborns is possible even with the use of spectral duplex scanning, the CDC greatly facilitates their examination. When using the EHD regime, you can visualize through the large fontanel, in the sagittal plane, under the calloused body, along the roof of the third ventricle, two large internal cerebral veins that merge into the Galen vein, which is not always located strictly midway, but is deflected more often to the right. Further along the middle line above the cerebellum is a straight sine; immediately under the bones of the skull and a large fontanel - the upper sagittal sinus. Very rarely, the lower sagittal and transverse sinuses are found. Evaluation of blood flow is also possible in the veins of the head of the caudate nucleus and thalamo-striatal veins, which are visualized in the parasagittal plane of scanning.

[1], [2], [3], [4], [5], [6], [7], [8]